Three congruent circles with centres P, Q and R are tangent to the sides of rectangle ABCD as shown. The circle with centre at Q has diameter 5cm and passes through the points P and R. Find the area of the rectangle ABCD.

Since each circle has diameter 5cm and the circle at Q passes through P and R, the centers P, Q, R are spaced 5cm apart along the length of the rectangle, giving a total length of $$3\times 5=15$$cm... actually the rectangle's dimensions work out to $$10\text{cm} \times 5\text{cm}$$ based on the circle arrangement shown in the figure. So the area is $$10 \times 5 = 50\text{ square cm}$$.