278,554 views
14 votes
14 votes
5 of the people on John's street know how to roller skate. 8 people know how to swim, and 3 people know both how to roller skate and how to swim. How many people know how to roller skate or how to swim or both?

User Thomas Enebo
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3.0k points

2 Answers

23 votes
23 votes

Explanation:


n(aub) = n(a) + n(b) - n(anb) \\ = 8 + 5 - 3 \\ = 8 + 2 \\ = 10 \\ thank \: you

User SimonAlfie
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2.3k points
9 votes
9 votes
  • A=people know how to roller skate
  • B =People know to swim
  • A intersection B=People know both
  • A union B=total people


\\ \sf\longmapsto n(A\cup B)=n(A)+n(B)-n(A\cap B)


\\ \sf\longmapsto 5+8-3


\\ \sf\longmapsto 13-8


\\ \sf\longmapsto 10

User Justin Wiseman
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3.2k points