Question

A triangle with vertices at A(20, –30), B(10, –15), and C(5, –20) has been dilated with a center of dilation at the origin. The image of B, point B prime, has the coordinates (2, –3). What is the scale factor of the dilation?

A. 1/0
B. 1/5
C. 5
D. 10

Answer 1

so when we're dilating, we're multiplying the x and y value by a number so we can either enlarge or shrink the size

Answer 2

so A was (20, -30)

and now A' is (2-, -3)

Answer 3

What number would you multiply to 20 to get 2

Or 30 to get -3

Answer 4

10 ?

Answer 5

You can use your answer choices to help you

Answer 6

So be careful now! We're trying to decrease the size

we're going from 20 to 2

we're not going from 2 to 20
yes, 2 * 10 = 20

but what number times 20 will get us 2?

Answer 7

let's say this number is x

x * 20 = 2

so what do you get when you divide 20 on both sides?

Answer 8

give me a few seconds to think-

Answer 9

4 ?? i dont even know-

Answer 10

okay okay

does 4 times 20 give you 2?

Answer 11

no-

Answer 12

what number do we have to divide 20 by to get 2

20 divided by what equals 2

Answer 13

20 divided y 2 = 10-

this is hard- i think im semi close tho-

Answer 14

yes

so the number is 10

BUT pay attention here

the scale factor is NOT 10
if it was 10
that would mean we are INCREASING
but for this question, we are DECREASING

we are going from 20 ---> 2
we are making it SMALLER

Answer 15

do you understand so far? we're close to the answer

Answer 16

sorta-

Answer 17

20 divided by 10 = 2- ??

Answer 18

so when we divide by a number

that's the same thing as multiplying by 1 over that number

so if we're dividing by 10

that means it's the same as multiplying by 1/10

Answer 19

does that make sense?

Answer 20

no- but Iĺl try and get it

Answer 21

What is 1/10

can you use a calculator and tell me what it is

Answer 22

I got 200- wait what-

Answer 23

oh wait, I multiplied

Answer 24

https://www.google.com/search?q=1%2F10

Answer 25

what is 1/10

Answer 26

sorry im slow-

Answer 27

don't divide by 20

I didn't ask you to divide by 20

I just asked you
what is 1/10

Answer 28

0.1

Answer 29

okay so just keep that in mind

let's go back to your question, okay?

Answer 30

Alright-

Answer 31

we're trying to find a number that we multiply the OLD points to get the NEW points

for example
(20, -30) was the old point

(2, -3) is the new point

we went from 20 to 2
we SHRUNK 20 to get 2

Answer 32

so what number MULTIPLIED by 20 will give us 2

remember that 0.1?

what is 20 * 0.1

Answer 33

2

Answer 34

looks like you just found your answer!!

remember 0.1 is the same thing as 1/10

Answer 35

Wait but there is no 2 on my answer options--

Answer 36

read my last message

Answer 37

again

Answer 38

OH SORRY ADSKHDASKJHADSKHJDSAHJKADSKHJD thank you.

Answer 39

there you go