Part of a toy is made of two rectangular blocks that are both 4 cm by 8 cm. One of the blocks turns about the other by a pin that goes through the centre of each block.
How much of the bottom block is covered by the top block?
When the top block turns it starts to cover more of the bottom block. What is the biggest area of the bottom block that is covered by the top block?
Solution
The top block covers a strip in the middle of the bottom block. This strip is 4cm wide. Since the bottom block is 8cm long the top block covers half of it.
When the top block has turned a quarter turn it will cover all of the bottom block.
Extension
If the top block is turned all the way around so that it finishes back where it starts, how many times does it cover the whole bottom block?