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  • The sum of first five multiples of 3 is (A) 45 (B) 55 (C) 65 (D) 75

The sum of first five multiples of 3 is

(A) 45

(B) 55

(C) 65

(D) 75

Answers (1)

\\$Given:- Multiple of 3 is : 3, 6, 9, 12, $ \ldots $ $ \ldots $ .\\$ a\textsubscript{1 }= 3, d = a\textsubscript{2} - a\textsubscript{1}\\ d = 6 - 3\\ d = 3\\ {{S}_{5}}=\frac{5}{2}[2{{a}_{1}}+(5-1)d] \\ =\frac{5}{2}(2\times 3+4\times 3) \\ =\frac{5}{2}(6+12) \\ =\frac{5}{2}\times (18) \\

Hence option A is correct.

Posted by

infoexpert21

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