Answer:
A. 300 cm²
Explanation:
Remember the formulae for the area A and circumference C of a circle:
A = r² π
C = 2π r
If we do the famous old engineering trick and just take π to be more or less equal to 3, we can easily find r:
C = 60 ≈ 2·3 r
⇒ r = 60/6 ≈ 10 [cm]
Then, using the same approximation for pi in the formula for area, we can find that:
A ≈ r²·3 = 10²·3 = 100·3 = 300
⇒ A ≈ 300 [cm²]
(The ≈ symbol pretty much means "is approximately equal to" by the way)