Exercise 989Combinatorics › Inclusion-exclusionL1Added 3 Nov 2026
Numbers coprime to $30$ up to $100$
#IE#coprime#totient
Statement
How many integers from to are coprime to ?
Hint
IE on divisibility by , , .
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Solution
From earlier. Numbers divisible by , , or : .
Complement. .
Conclusion. integers are coprime to .
Check. Pattern period : per period; . In each full period , so ; in the last , coprime to : — but only are . So . ✓