Question

After a dilation with a center of (0, 0), a point was mapped as (4, –6) → (12, y). A student determined y to be –2. Evaluate the student's answer.

A.
The student is correct.
B.
The student incorrectly calculated the scale factor to be –2.
C.
The student incorrectly divided by the scale factor instead of multiplying by it.
D.
The student incorrectly added the scale factor instead of multiplying by it.

Answer 1

Hint: If we dilate the point (x,y) about (0,0) by a scale factor of a, then the new point should be (ax,ay).

Answer 2

looking at just the x-coordinates of your point and your new point what did 4 get multiplied by?

Answer 3

2?

Answer 4

so 4(2) is 12?

Answer 5

3 lol

Answer 6

yes 4(3)=12
and you have just figured out what the scale factor is

Answer 7

3 is the scale factor

Answer 8

3 is what you want to multiply x and y by to get the new point

Answer 9

so let me change my hint a little bit since we know that a above is now 3


Hint: If we dilate the point (x,y) about (0,0) by a scale factor of 3, then the new point should be (3x,3y).

Answer 10

so you had (4,-6)->(4*3,-6*3)

Answer 11

(4,-6)->(12,-18)?

Answer 12

that's right

Answer 13

now you just need to figure out what the student did to get -2

Answer 14

so the scale factor was 3

did he add the scale factor or divide by the scale factor?
that is did he do -6/3 or -6+(3)

Answer 15

-6/3 = -2 so therefore he divided instead of multiplying?

Answer 16

yah

Answer 17

yay! thanks :) it helped a lot!!!

Answer 18

but I also don't see what is wrong with b

I just think c provides more evaluation

Answer 19

like b says he is just wrong and I'm not going to give a reason
while c says he is wrong but I will give a reason

Answer 20

yeah it does because he divided wrong so therefore -2 shouldnt be the answer

Answer 21

right I think that explains why you are marking the problem wrong (this is more of an evaluation in my mind)

Answer 22

yeah it is..

Answer 23

anyways have fun :)

Answer 24

lol always! :) you too