Question 18
The diagram shows three semi-circles inside a rectangle. The semi-circle in the middle touches the other two semi-circles, which each touch a short side of the rectangle. The biggest semi-circle also touches the upper long side of the rectangle. The shortest distances from that side of the rectangle to the two other semi-circles are 5 cm and 7 cm, respectively (see diagram). How big is the perimeter of the rectangle in cm? 