At a school swimming meet, 1/3 of the pupils were boys. Given that 2/5 of the boys and 3/5 of the girls did not know how to swim, how many pupils were there altogether if there were 490 swimmers at the swimming meet?
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2 answers
2/5 of the boys don't know how to swim, so 2/5 * 1/3= 2/15 of the total people are boys who cannot swim. Likewise for girls, 3/5 * 2/3= 6/15 of the total people are girls who cannot swim. Thus, 1- 2/15 - 6/15= 7/15 of the total people are swimmers. Thus, there are 490 swimmers and there are 15/7 * 490= 1050 pupils in total.
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