A Toy Problem 1

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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.

toy.
 
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?