Sum of multiples of 3 or 5

MediumBrainteasers~4m

What is the sum of all integers from 1 to 100 that are divisible by 3 or by 5?

Show hints (2)+
  1. Inclusion–exclusion: add multiples of 3 and of 5, then subtract the overlap.
  2. The overlap is multiples of lcm(3,5)=15\mathrm{lcm}(3,5)=15, not 3+53+5.

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2418

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Asked at: Timed Mental-Math & Sequences, Game-Based Aptitude

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