This is a tricky question from Singapore's PSLE. I don't think I would have solved it easily in a timed exam. So let's work it out carefully in our own time. Thanks to Jul, Abdul, and Junwen for the suggestion!

References
https://mothership.sg/2021/10/psle-coin-question/
https://cnalifestyle.channelne....wsasia.com/living/ps

Other problems from Singapore
Area of a claw
https://www.youtube.com/watch?v=B_yNI3gAHNk&t=1s
Overlapping circles in a circle
https://www.youtube.com/watch?v=fpdIdtYg4YE&t=1s
Students cried after this question
https://www.youtube.com/watch?v=Xrx8oa8NeXI
Cheryl's birthday
https://www.youtube.com/watch?v=2yeEmqUfI6U&t=1s
Overlapping semicircles in a rectangle
https://www.youtube.com/watch?v=TOf35SRT1A4

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