This question appeared during the Primary School Leaving Examination 2019. It shocked 12-year-old kids and got anxious parents all fired up.
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34 sats \ 1 reply \ @Murch 29 Sep
3d+2×12 = 2d +16+2×22 | - 2d - 24
3d+2×12 - 2d - 24 = 2d +16 + 44 - 2d - 24
d = 36
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0 sats \ 0 replies \ @cryotosensei OP 29 Sep
Well done!
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135 sats \ 1 reply \ @Bell_curve 29 Sep
Diameter is 16 + 10 + 10?
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21 sats \ 0 replies \ @cryotosensei OP 29 Sep
Yes! Great job
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24 sats \ 1 reply \ @south_korea_ln 29 Sep
I can understand why some 12-year-olds would get stressed having to solve one of these. The math isn't complicated, but it's about having the right insight when time is of the essence. Reminds me of the Math Olympiads when I was 16 or so... a bit more maturity at the time than a 12-year old, but still, very stressful.
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0 sats \ 0 replies \ @cryotosensei OP 30 Sep
Wow! You represented South Korea? Impressive
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