Find the sum of all 2-digit natural numbers divisible by 5.

Question

KnowledgeBoat · Accepted Answer

The 2-digit natural numbers divisible by 5 form an A.P., with common difference = 5. 10, 15, 20,.....,95 Let total number of terms in an A.P. be n. We know that, ∴ an = a + (n - 1)d ⇒ 95 = 10 + (n - 1)5 ⇒ 95 - 10 = (n - 1)5 ⇒ 85 = (n - 1)5 ⇒ = (n - 1) ⇒ 17 = (n - 1) ⇒ n = 17 + 1 ⇒ n = 18. We know that, Sum of n terms of an A.P. is given by, ∴ Sn = (a + l) ⇒ S18 = = 9(105) = 945. Hence, S18 = 945.

Mathematics

Find the sum of all 2-digit natural numbers divisible by 5.

AP

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Mathematics

Find the sum of all 2-digit natural numbers divisible by 5.

AP

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