Question

I would appreciate I someone could help me with these questions

Answer 1

38: it's a right triangle
39:
area:
$a = \pi {r}^{2}$
$a = 3.14 \times {10}^{2} = 314$

circumference:
$c = \pi \times diameter$
$c = 3.14 \times 20 = 62.8$