This problem comes from a national exam in Malaysia. A cylindrical container with length 20 cm is placed on the floor against the wall as shown in the diagram. Point Q is on the edge of the base and Q is 2 cm from the wall and 1 cm from the floor. Can the cylindrical container fit inside a box whose dimensions are 21 cm × 7 cm × 7 cm? Why or why not? Assume the wall and floor are perpendicular.

Thanks to the person who emailed me this!

[Update 5 Feb 2018] Here's a solution from a teacher in Malaysia which is very similar to the solution I presented:
https://www.facebook.com/maths.video/photos/a.581783621835231.146536.503727749640819/1847702531909994/?type=3&theater

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