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Find the Sum of First 12 Natural Numbers Each of Which is a Multiple of 7. - Mathematics

Sum

Find the sum of first 12 natural numbers each of which is a multiple of 7.

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Solution

First 12 natural numbers which are multiples of 7 are as follows

7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84

Clearly thus forms an A.P with first term a = 7, common difference d = 7 and last term l = 84

Sum of first n terms = `S = n/2 [a + l]`

=> Sum of first 12 natural numbers whihc are  multiple of  7 = `12/2 [7 + 84]`

= 6 x 91

= 546

Concept: Arithmetic Progression - Finding Sum of Their First ‘N’ Terms.
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APPEARS IN

Selina Concise Maths Class 10 ICSE
Chapter 10 Arithmetic Progression
Exercise 10 (C) | Q 4.2 | Page 143
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