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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 an arithmetic progression (AP) approach. The smallest two-digit number divisible by 3 is 12, and the largest is 99. These numbers form an arithmetic sequence with a common difference of 3.

  • 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. This is confirmed by multiple sources, including Byju's (https://byjus.com/question-answer/how-many-two-digit-numbers-are-divisible-by-3-10/), LearnAtNoon (https://www.learnatnoon.com/s/in/how-many-two-digits-numbers-are-divisible-by-3/61575/), and others cited in the references. These sources corroborate the use of arithmetic progressions to efficiently determine the count.

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