Question

Find the circumference and the area of a circle that has a diameter of 8.4 meters.

Answer 1

The area of a circle with respect to its diameter is:

a=(πd^2)/4, we are told d=8.4 so

a=8.4^2π/4

a=17.64π m^2

a≈55.42 m^2  (to nearest hundredth of a square meter)

C=πd, again d=8.4m so

C=8.4π m

C≈26.39 m (to nearest hundredth of a meter)

Answer 2

To find the circumference of a circle, simply multiply the diameter by pi. 
The answer (depending on how you teacher wants it) is either 8.4$\pi$ or 26.39.

You teacher most likely wants to see 26.39 as the diameter



The area can be found by squaring the radius and multiplying it by pi.
The radius is 4.2, so...
$4.2^{2} * \pi ...............$
$17.64 * \pi...............$
The area is 55.39