Here’s a warm up joke:
Three logicians walk into a bar. The bar tender asks “Do all of you want a drink?”
The first logician says, “I don’t know.”
The second logician says, “I don’t know.”
The third logician says, “Yes!”
The following question went viral on Facebook. It had a sensationalising title: “Primary 5 [11 year old] mathematics question”, which later turned out to be incorrect as it was actually a Secondary 3 [15 year old] maths olympiad question.
I didn’t give much though to this question when I first saw it because I have seen such questions before so it wasn’t something new. But someone shared this with me in a private chat and so I thought might as well write a short blog post about how I solved it.