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Find the Sum of First 8 Multiples of 3 - CBSE Class 10 - Mathematics

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Question

Find the sum of first 8 multiples of 3

Solution 1

First, 8 multiples of 3 are { 3, 6, 9...,24}

We can observe they are in AP with first term (a) = 3 and last term (l) = 24 and number of terms are 8.

`S_n = n/2 (a + l)`

`=> S_n = 8/2(3 + 24)`

`S_8 = 4 xx (3 + 24) = 108`

Hence, the sum of the first 8 multiples of 3 is 108

 

Solution 2

First 8 multiples of 3 are

3, 6, 9, 12, 15, 18, 21, 24

The above sequence is an A.P

a= 3, d= 3 and last term l = 24

`S_n = n/2 (a + 1) = 8/2[3 + 24] = 4(27)`

`S_n = 108`

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Solution Find the Sum of First 8 Multiples of 3 Concept: Sum of First n Terms of an AP.
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