Q9 of 105 Page 146

Find the sum of the first 40 positive integers divisible by 6.

The first 40 positive integers divisible by 6 are,

6, 12,…..240


Here we have n = 40 terms


First term (a) = 6;


Common difference is 6 since they are multiple of 6


The sum of 6 terms is given by (sn) = [2a + (n-1) d]


S6 = [2×6 + (40-1)6]


= 4920


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