Answer:
Step-by-step explanation:
There are two great ways to set up this problem and they both get you the same answer. First you know that the triangles are similar, this means they are the same shape, but not necessarily the same size. You can use ratios to compare the sizes of the sides. Just be sure to compare like things to like things.
One way: compare the small triangle's long side to short leg with the big triangle's long side to short leg. Like this:
13/5 = 39/a
OR...compare long side(sm) to long side(big) compared to short leg(sm) to short leg(big). Like this:
13/39 = 5/a
Amazingly, these equations will give you the same answer.
13a = 39*5
13a = 195
13a/13 = 195/13
a = 15
You can maybe see that the big triangle's side is 3 times bigger than the small one (13 times 3 is 39) So it works out that the 5 on the little triangle is 3 times bigger--15--on the large triangle!
