Find the sum of all multiples of 9 lying between 300 and 700.

Question

KnowledgeBoat · Accepted Answer

The sum of all multiples of 9 lying between 300 and 700 is 306 + 315 + ..... + 693. The above series is an A.P. with a = 306, d = 9 and l = 693. Let 693 be nth term of the series then, ⇒ 693 = 306 + 9(n - 1) ⇒ 693 - 306 = 9n - 9 ⇒ 387 = 9n - 9 ⇒ 9n = 387 + 9 ⇒ 9n = 396 ⇒ n = 44. By formula S_n = ⇒ S₄₄ = ⇒ S₄₄ = 22[612 + 387] ⇒ S₄₄ = 22 × 999 ⇒ S₄₄ = 21978. Hence, the sum of all multiples of 9 lying between 300 and 700 is 21978.

Mathematics

Find the sum of all multiples of 9 lying between 300 and 700.

AP GP

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