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Answer:
The sum of all positive integers less than 100, which are not divisible by 3 is 3267.
Step-by-step explanation:
The all positive integers less than 100 has sum, given by
S₁ = 1 + 2 + 3 + 4 + ......... + 99
⇒ S₁ =
Now, the sum of all positive integers less than 100 which are divisible by 3 is
S₂ = 3 + 6 + 9 + 12 + 15 + ........ + 99
⇒ S₂ = 3(1 + 2 + 3 + ........ + 33)
⇒ S₂ =
Therefore, the sum of all positive integers less than 100, which are not divisible by 3 is = S₁ - S₂ = 4950 - 1683 = 3267. (Answer)
Note : The sum of n natural numbers S is given by
S = 1 + 2 + 3 + 4 + ....... + n = .