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How Many Two-Digit Numbers Are Divisible by 3?

Published in Number Theory 1 min read

There are 30 two-digit numbers divisible by 3.

This can be solved using the concept of arithmetic progression (AP). The two-digit numbers divisible by 3 form an arithmetic sequence: 12, 15, 18, ..., 99.

  • First term (a): 12
  • Common difference (d): 3
  • Last term (l): 99

We can use the formula for the nth term of an AP: l = a + (n-1)d, where 'n' is the number of terms.

Solving for 'n':

99 = 12 + (n-1)3
87 = (n-1)3
29 = n-1
n = 30

Therefore, there are 30 two-digit numbers divisible by 3. Multiple sources (Byjus, Shaalaa, Doubtnut, Teachoo, LearnAtNoon, Unacademy) confirm this result.

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