Multiple choice

The sum of all natural numbers from 100 to 300 which are exactly divisible by 4 and 5 is

  1. 2200

  2. 2000

  3. 2220

  4. None of these

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A Correct answer
Explanation

Numbers divisible by both 4 and 5 are divisible by LCM(4,5)=20. Multiples of 20 from 100 to 300 are: 100, 120, ..., 300. This is 11 terms. Sum = 11/2 × (100 + 300) = 11/2 × 400 = 2200.