How do you solve an area of a circle word problem?

Question

Easy:

Lola works at a lab with a huge circular particle accelerator. It has a diameter of 6 kilometres. What is the accelerator's circumference?

Hard:

A metalworker cuts out a large semicircle with a diameter of 28 centimetres. Then the metalworker cuts a smaller semicircle out of the larger one and removes it. The diameter of the semicircular piece that is removed is 14 centimetres. Find the distance around the shape after the smaller semicircle is removed.

Answer 1

circumference = pi x diameter = 6pi = about 6(3.14 = 18.84 km

28pi/2 + 14pi/2 + 14 = 42pi/2 + 14 = 21pi +14 = about 21(3.14) +14 = 65.94 +14 = 79.94 = the inside perimeter + the outside perimeter of what's left