Number TheoryDivisibility★☆☆☆☆Easy+20 XP
What is the remainder when 24 is divided by 5?
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Number Theory
Divisibility, mods, primes.
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Number TheoryDivisibility★★★☆☆Hard+40 XP
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Number TheoryDivisibility★★★☆☆Hard+40 XP
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Premium problem
How many positive integers less than 36 are relatively prime to 36? (This is φ(36).)
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