Do the ratios have to have the same scale factor to be a dilation? My friend says yes, or else the scale factor would be useless. I on the other hand say no because it's still a dilation as it's an reduction.

Here's the instructions: "For Exercises 5-8, tell whether one figure is a dilation of the other or not. If one figure is a dilation of the other, tell whether it is an enlargement or a reduction. Explain your reasoning."

And here's the problem I answered to be a reduction: "Triangle R'S'T' has sides of 3 cm, 4 cm, and 5 cm. Triangle RST has sides of 12 cm, 6 cm, and 25 cm."

5 answers

Also does my explanation sound plausible? I answered reduction and my reasoning was "because the scale factor of each coordinate[/ratio] is less than 1 and more than 0 (decimal)".
your friend is right, you have failed to see that a dilation with a scale factor less than one is a reduction.
I guess you didn't see my second post before answering. But then, I did say in my first post, " I on the other hand say no because it's still a dilation as it's an reduction." Sorry for late reply because I had to catch the bus (I was using the library's WIFI to post this question & I don't have data to use a network).

I forgot to include the scale factors I got for each ratio: image/preimage. So for 3/12 it is 0.25, 4/16 (typo in first post) is 0.25, and 5/25 is 0.20(!). The last ratio is what's bothering me. Because one is different from the others, does it still make it a dilation? That's what I was asking.
Where are my manners? I forgot to say thank you for answering my question.
I guess I'll just get answers from an answer key.