Answer: DE is 15 and AB is 6
Explanation:
Okay, so when two shapes are similar, that means they are proportional. Look at the sides. Notice how the lengths of each side on the larger triangle are all multiples of the lengths of the smaller triangle (side CE, for example, is 24, and AC is 8 since 24 is 3 times larger than 8, you know that particular side was dilated by 3x).
Since these are similar, but not congruent, you know that the dilation was applied to the entire shape equally. In other words, each side is dilated by 3 or is 300% larger.
So, to find DE, just multiply the corresponding side, BC, by 300%.
5*300% (or just 5*3) is 15. So, DE is 15cm long. Make sense?
For AB, you know the scale factor is 3, so you have to figure what number times 3 will get you 18. Because 6*3 is 18, you know AB has to be 6.