Your technique is sound, so assuming you pressed the right buttons on your calculator, you're correct.
Use the figure to find the approximate perimeter of RSTU.
A) 72.5 in.
B) 73.6 in.
C) 72.0 in.
D) 73.0 in.
E) 71.8 in.
you have to find the length of the sides first since its not given,
use a^2+b^2 = c^2 to find the side you need
from the picture, you have a right triangle so, 15^2 + 5^2 = c^2
solve for c = 5 sq root(10)
Perimeter is the sum of the 4 sides: 2a+2b= [2*5sq root(10)] + [2*(16+5)]