The Official Homework Help Thread!

[pimo]

 

A man travels 3 blocks west, 3 blocks north, and then 4 blocks east. 

(a) What is his resultant displacement?

 

 

_____ blocks at _____° counterclockwise from east.

 

try drawing a diagram, do you have to use trig for this question?

[Mango]

try drawing a diagram, do you have to use trig for this question?

im not sure, we just started this chapter but im just working ahead so do my work for me pls n thanks, i love my fangoes 

 

nvm i found the answer by myself

Edited September 21, 2015 by Mangojuice

[pimo]

im not sure, we just started this chapter but im just working ahead so do my work for me pls n thanks, i love my fangoes 

do you know how to draw the vector diagram? draw and add the vectors, then using trig you can find the rest

 

 

anyone know how to draw tangent lines to a graph on excel? 

[BAP_STARLIGHT]

I need more help. Please help me. Thank you!

 
1.At a convention, each guest was given a ticket. 40% of the guest received red tickets, 3/8 received blue tickets, 20 percent green tickets, and 20 guest received yellow tickets. How many guest attended the convention received blue tickets?

2.Three pencils and two erasers cost $0.60. Two pencils and three erasers cost $0.55. How much will it cost to buy 7 pencils and erasers?

 

3. A student's grade improved 20% over the grade for the marking period. If the student's current grade for the previous marking period? 

 

4. Six students took a test. The arithmetic mean of their was 84. 5 of the scores were 68,92,90,86 and 72. What is the sixth score? 

[pimo]

I need more help. Please help me. Thank you!

[font='Helvetica Neue']1.At a convention, each guest was given a ticket. 40% of the guest received red tickets, 3/8 received blue tickets, 20 percent green tickets, and 20 guest received yellow tickets. How many guest attended the convention received blue tickets?[/font]
[font='Helvetica Neue']2.Three pencils and two erasers cost $0.60. Two pencils and three erasers cost $0.55. How much will it cost to buy 7 pencils and erasers?[/font]

[font='Helvetica Neue']3.[/font][font='Helvetica Neue'] A student's grade improved 20% over the grade for the marking period. If the student's current grade for the previous marking period? [/font]

[font='Helvetica Neue']4. Six students took a test. The arithmetic mean of their was 84. 5 of the scores were 68,92,90,86 and 72. What is the sixth score? [/font]

for number 4, multiply 84.5 by 6. Then subtract all the known scores from that number, you're left with the last kids score

[Guardian of the Galaxy]

I need more help. Please help me. Thank you!

 
1.At a convention, each guest was given a ticket. 40% of the guest received red tickets, 3/8 received blue tickets, 20 percent green tickets, and 20 guest received yellow tickets. How many guest attended the convention received blue tickets?

2.Three pencils and two erasers cost $0.60. Two pencils and three erasers cost $0.55. How much will it cost to buy 7 pencils and erasers?

 

3. A student's grade improved 20% over the grade for the marking period. If the student's current grade for the previous marking period? 

 

4. Six students took a test. The arithmetic mean of their was 84. 5 of the scores were 68,92,90,86 and 72. What is the sixth score? 

 

1. You are told the amount of red, blue and green tickets received as a proportion (whether it be a fraction or a percentage) of the whole, while you are told the amount of yellow tickets received as an absolute amount. Therefore we can figure out the proportion of yellow tickets received as it is what's left over when adding the proportions represented by the other three.

 

Red - 40% = 0.4

Blue - 3/8 = 0.375

Green - 20% = 0.2

Yellow - 1 - (0.4 + 0.375 - 0.2) = 0.025 = 2.5%

 

So you know that 2.5% of the tickets are yellow, and that means 20 tickets. You can find how many tickets were given in total by dividing the amount (20) by the proportion (2.5% = 0.025), since the total amount multiplied by the proportion of yellow would give you the amount of yellow.

 

20/0.025 = 800 tickets in total

 

Now you can find out how many blue tickets were given:

 

3/8 * 800 = 300 blue tickets

 

2. This is a system of linear equations. You have two unknowns (price of the eraser - E, and price of the pencil, P) and two equations (3P + 2E = 0.6 and 2P + 3E = 0.55). As long as you have more (linearly independent) equations than unknowns, you can find a solution for the system. (If you don't know what linear independence is, you don't have to for this question; these two equations are, however.)

 

You can solve for one of the unknowns by manipulating the given equations until you can eliminate one of the unknowns. (This is called the method of elimination). Do this by making the coefficients (the number before the unknown) equal in both equations.

 

Equation 1: 3P + 2E = 0.6

Equation 2: 2P + 3E = 0.55

 

If you multiply Eq. (1) by 3 and multiply Eq. (2) by 2,

(1): 9P + 6E = 1.8 -- call this Eq. (3)

(2): 4P + 6E = 1.1 -- call this Eq. (4)

 

Subtract Eq. (4) from Eq. (3) to eliminate E and find P.

(3) - (4): 5P = 0.7

P = 0.14

 

So a pencil costs 14 cents. Now you can go back to one of your original equations to find E. Let's do equation (1).

 

(1): 3(0.14) + 2E = 0.6

2E = 0.18

E = 0.09

 

Now you need to know how much 7 pencils and erasers, i.e., 7P + 7E. Substituting in P = 0.14 and E = 0.09 gives:

7(0.14) +  7(0.09) = 1.61

 

3. It appears as if this question has incomplete information. Does the question tell you either grade?

Edited September 21, 2015 by a232313

[BAP_STARLIGHT]

1. You are told the amount of red, blue and green tickets received as a proportion (whether it be a fraction or a percentage) of the whole, while you are told the amount of yellow tickets received as an absolute amount. Therefore we can figure out the proportion of yellow tickets received as it is what's left over when adding the proportions represented by the other three.

 

Red - 40% = 0.4

Blue - 3/8 = 0.375

Green - 20% = 0.2

Yellow - 1 - (0.4 + 0.375 - 0.2) = 0.025 = 2.5%

 

So you know that 2.5% of the tickets are yellow, and that means 20 tickets. You can find how many tickets were given in total by dividing the amount (20) by the proportion (2.5% = 0.025), since the total amount multiplied by the proportion of yellow would give you the amount of yellow.

 

20/0.025 = 800 tickets in total

 

Now you can find out how many blue tickets were given:

 

3/8 * 800 = 300 blue tickets

 

2. This is a system of linear equations. You have two unknowns (price of the eraser - E, and price of the pencil, P) and two equations (3P + 2E = 0.6 and 2P + 3E = 0.55). As long as you have more (linearly independent) equations than unknowns, you can find a solution for the system. (If you don't know what linear independence is, you don't have to for this question; these two equations are, however.)

 

You can solve for one of the unknowns by manipulating the given equations until you can eliminate one of the unknowns. (This is called the method of elimination). Do this by making the coefficients (the number before the unknown) equal in both equations.

 

Equation 1: 3P + 2E = 0.6

Equation 2: 2P + 3E = 0.55

 

If you multiply Eq. (1) by 3 and multiply Eq. (2) by 2,

(1): 9P + 6E = 1.8 -- call this Eq. (3)

(2): 4P + 6E = 1.1 -- call this Eq. (4)

 

Subtract Eq. (4) from Eq. (3) to eliminate E and find P.

(3) - (4): 5P = 0.7

P = 0.14

 

So a pencil costs 14 cents. Now you can go back to one of your original equations to find E. Let's do equation (1).

 

(1): 3(0.14) + 2E = 0.6

2E = 0.18

E = 0.09

 

Now you need to know how much 7 pencils and erasers, i.e., 7P + 7E. Substituting in P = 0.14 and E = 0.09 gives:

7(0.14) +  7(0.09) = 1.61

 

3. It appears as if this question has incomplete information. Does the question tell you either grade?

Sorry i missed one part 

3. A student's grade improved 20% over the grade for the marking period. If the student's current grade is 90, what was the grade for the previous marking period? 

[pimo]

Sorry i missed one part 
3.[font='Helvetica Neue', Helvetica, Arial, sans-serif] A student's grade improved 20% over the grade for the marking period. If the student's current grade is 90, what was the grade for the previous marking period? [/size][/font]

Well his new grade is his old grade times 120%
Old grade x 1.2=90
Old grade =90/1.2

[VANTE]

can anyone help me with korean?

[Mango]

i must've missed something in the notes because i have no idea how to get the second part! 

[pimo]

i must've missed something in the notes because i have no idea how to get the second part! 

soo the stone is unifromly accelerating (because of gravity)

state your givens then find the equation you need to use out of the 5 equations for uniform motion

 

t = 3.41

d = -57

a = -9.8 (gravity)

vf = ?

 (Im just gonna call Vfinal v in the calculations)

 

 

d= vt - (at^2)(0.5)

-57 = 3.41v - (-9.8)(3.41)^2 * (0.5)

-57 =3.41v + 56.98

-114/3.41 = v

v = -33.4

 

since its speed no need for the negative direction so it should be 33.4 m/s  yikes sorry

I only calculated the vertical component, the horizontal is 16 m/s

you need to find the resultant velocity by adding the vectors (using pythagorean theorem or the parallelogram way)

Edited September 22, 2015 by pimo

[Mango]

state your givens then find the equation you need to use

t = 3.41

d = -57

a = -9.8 (gravity)

vf = ?

 (Im just gonna call Vfinal v in the calculations)

 

d= vt - (at^2)(0.5)

-57 = 3.41v - (-9.8)(3.41)^2 * (0.5)

-57 =3.41v + 56.98

-114/3.41 = v

v = -33.4

 

since its speed no need for the negative direction so it should be 33.4 m/s

it says thats wrong n now i have no more chances to submit a new answer 

but thanks anyway pimo

Edited September 22, 2015 by Mangojuice

[pimo]

it says thats wrong n now i have no more chances to submit a new answer 

but thanks anyway pimo

omg sorry 

good luck with physics, Im doing the same unit rn

[pimo]

it says thats wrong n now i have no more chances to submit a new answer 

but thanks anyway pimo

btw how did you get your first answer?

[Guardian of the Galaxy]

i must've missed something in the notes because i have no idea how to get the second part! 

 

I'm guessing you haven't gotten to Conservation of Energy yet, but you can find the answer using kinematics. Remember the "Big Five" kinematics equations:

 

 

Note that there are five variables involved: d (displacement), v_i (initial velocity), v_f (final velocity), a (acceleration), and t (time), Each of the five equations includes four of those variables, so as long as you know three of them you can figure out another.

 

Also you have to break this down into components; the x-direction (horizontal - the direction the person kicked the stone at 16 m/s at) and the y-direction (vertical - the direction the stone is falling). If you do a free-body diagram the only force acting on the stone (ignoring air resistance) is gravity, so no matter what its velocity in the x-direction (call it v_x) is always 16 m/s. In the y-direction, its initial velocity is 0 m/s and increases as it falls.

 

We can use equation 3 to find the final y-direction velocity of the stone:

v_f_y = v_i_y + a*t

v_f_y = 0 + 9.8*3.41 = 33.42 m/s

 

Given that the x-direction and y-direction are perpendicular, you can calculate the magnitude of the total velocity using Pythagoras' Theorem:

 

v^2 = (v_x)^2 + (v_y)^2

 

Knowing that when the stone hits the water, v_y = 33.42 m/s and v_x = 16 m/s:

 

v = sqrt(33.42^2 + 16^2) = 37.05 m/s

[pimo]

I'm guessing you haven't gotten to Conservation of Energy yet, but you can find the answer using kinematics. Remember the "Big Five" kinematics equations:

 

 

Note that there are five variables involved: d (displacement), v_i (initial velocity), v_f (final velocity), a (acceleration), and t (time), Each of the five equations includes four of those variables, so as long as you know three of them you can figure out another.

 

Also you have to break this down into components; the x-direction (horizontal - the direction the person kicked the stone at 16 m/s at) and the y-direction (vertical - the direction the stone is falling). If you do a free-body diagram the only force acting on the stone (ignoring air resistance) is gravity, so no matter what its velocity in the x-direction (call it v_x) is always 16 m/s. In the y-direction, its initial velocity is 0 m/s and increases as it falls.

 

We can use equation 3 to find the final y-direction velocity of the stone:

v_f_y = v_i_y + a*t

v_f_y = 0 + 9.8*3.41 = 33.42 m/s

 

Given that the x-direction and y-direction are perpendicular, you can calculate the magnitude of the total velocity using Pythagoras' Theorem:

 

v^2 = (v_x)^2 + (v_y)^2

 

Knowing that when the stone hits the water, v_y = 33.42 m/s and v_x = 16 m/s:

 

v = sqrt(33.42^2 + 16^2) = 37.05 m/s

oh i forgot about the horizontal thingy!! so sorry mango T^T. thanks for this answer

[Mango]

I'm guessing you haven't gotten to Conservation of Energy yet, but you can find the answer using kinematics. Remember the "Big Five" kinematics equations:

 

 

Note that there are five variables involved: d (displacement), v_i (initial velocity), v_f (final velocity), a (acceleration), and t (time), Each of the five equations includes four of those variables, so as long as you know three of them you can figure out another.

 

Also you have to break this down into components; the x-direction (horizontal - the direction the person kicked the stone at 16 m/s at) and the y-direction (vertical - the direction the stone is falling). If you do a free-body diagram the only force acting on the stone (ignoring air resistance) is gravity, so no matter what its velocity in the x-direction (call it v_x) is always 16 m/s. In the y-direction, its initial velocity is 0 m/s and increases as it falls.

 

We can use equation 3 to find the final y-direction velocity of the stone:

v_f_y = v_i_y + a*t

v_f_y = 0 + 9.8*3.41 = 33.42 m/s

 

Given that the x-direction and y-direction are perpendicular, you can calculate the magnitude of the total velocity using Pythagoras' Theorem:

 

v^2 = (v_x)^2 + (v_y)^2

 

Knowing that when the stone hits the water, v_y = 33.42 m/s and v_x = 16 m/s:

 

v = sqrt(33.42^2 + 16^2) = 37.05 m/s

thanks! 

[Mango]

[Guardian of the Galaxy]

 

The shortest path across the river would be directly across, from bank-to-bank, but the river flows perpendicularly to this direction. If the hunter steered his boat directly across the river he would be carried by the current further downstream. Therefore, the hunter will have to point his boat in a diagonal direction against the flow of the river so that his path ends up being straight across.

 

Let's call the "across" direction 'x', with the positive direction in the way the hunter wants to go and the "flow" direction 'y', with the positive direction being upstream (i.e., against the flow of the river)

 

v_water = -5.7 km/h

-- v_water is entirely in the y-direction

 

v_total = v_boat + v_water; break v_boat into x and y components; you're given that the magnitude of v_boat is 11.2 km/h.

v_boatx = ?

v_boaty = ?

v_boatx^2 + v_boaty^2 = 11.2 km/h

 

You want the y-component of the boat's velocity to cancel out the flow of the river; therefore, v_boaty = 5.7 km/h. Using Pythagoras' theorem, v_boatx = 9.64 km/h.

 

Since v_boaty and v_water cancel out, v_total = v_boatx. So the hunter travels at 9.64 km/h across the river, and it takes him 2.5/9.6 * 60 = 15.6 min.

[Mango]

The shortest path across the river would be directly across, from bank-to-bank, but the river flows perpendicularly to this direction. If the hunter steered his boat directly across the river he would be carried by the current further downstream. Therefore, the hunter will have to point his boat in a diagonal direction against the flow of the river so that his path ends up being straight across.

 

Let's call the "across" direction 'x', with the positive direction in the way the hunter wants to go and the "flow" direction 'y', with the positive direction being upstream (i.e., against the flow of the river)

 

v_water = -5.7 km/h

-- v_water is entirely in the y-direction

 

v_total = v_boat + v_water; break v_boat into x and y components; you're given that the magnitude of v_boat is 11.2 km/h.

v_boatx = ?

v_boaty = ?

v_boatx^2 + v_boaty^2 = 11.2 km/h

 

You want the y-component of the boat's velocity to cancel out the flow of the river; therefore, v_boaty = 5.7 km/h. Using Pythagoras' theorem, v_boatx = 9.64 km/h.

 

Since v_boaty and v_water cancel out, v_total = v_boatx. So the hunter travels at 9.64 km/h across the river, and it takes him 2.5/9.6 * 60 = 15.6 min.

it says thats wrong?

[Guardian of the Galaxy]

it says thats wrong?

 

I made the assumption that he wants to end up directly across where he currently is, and that the river flows perpendicularly to the width of the river. If he uses the power from his boat entirely in the x-direction, he'll cross the river in 2.5/11.2 * 60 = 13.4 min but he'll end up further downstream.

[exoticinspirit]

Please help me figure out how to do this

[spoiler][/spoiler]

 

Basic math is not my strong point

 

 

Edit: Plugged in random numbers until they worked lmfao 

Edited September 24, 2015 by exoticinspirit

[pimo]

Please help me figure out how to do this

[spoiler][/spoiler]

 

Basic math is not my strong point

 

 

Edit: Plugged in random numbers until they worked lmfao 

I feel like plugging in random numbers would be quicker than the algebraic way to solve these lol

but if you want to know the algebraic way : (sorry if the explanation makes no sense)

[spoiler]

ex question 1

you can name the two unknowns x and y.

x+y = 2

xy= -15

 

there are many ways to solve this, one way is to choose one equation and isolate one variable.

(im rearranging the first one)

x = 2 -y

 

now use this (2-y) instead of x in the second equation

(2-y)y = -15

 

2y - y^2 = -15

 

now this is a quadratic equation, so youd solve by factoring or whatever you want

 

0 = y^2 -2y -15

0 = (y+3)(y-5)

so y= -3 or y = 5

 

if y is -3, then x is 5.

or if y is 5, x is -3.

 

so the two numbers are 5 and -3

[/spoiler]

[exoticinspirit]

I feel like plugging in random numbers would be quicker than the algebraic way to solve these lol

but if you want to know the algebraic way : (sorry if the explanation makes no sense)

[spoiler]

ex question 1

you can name the two unknowns x and y.

x+y = 2

xy= -15

 

there are many ways to solve this, one way is to choose one equation and isolate one variable.

(im rearranging the first one)

x = 2 -y

 

now use this (2-y) instead of x in the second equation

(2-y)y = -15

 

2y - y^2 = -15

 

now this is a quadratic equation, so youd solve by factoring or whatever you want

 

0 = y^2 -2y -15

0 = (y+3)(y-5)

so y= -3 or y = 5

 

if y is -3, then x is 5.

or if y is 5, x is -3.

 

so the two numbers are 5 and -3

[/spoiler]

It was, I got a few wrong (which is weird bc it worked), but yeah my teacher said he just plugged them in randomly lol

Thank you though <3 

Edited September 27, 2015 by exoticinspirit

[oh-gumdrop]

Helpppp please
Can you solve for a? Idk why it wont work
I tried using the method i used for previous questions and got them right, idk why it aint working now :'(
(2a -1)^2 - (a - 3)(a + 3) = 3a(a- 1)