Question

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

Answer 1

Answer:

55

Step-by-step explanation:

The first five multiples of 3 are:

3,6,9,12,15

SUM=3+6+9+12+15

=45

Answer 2

$\large\bold{ \underline{ \underline{ \: \: \: Answer \: \: \: }}}$

$\implies$ Correct Option is A

$\large\bold{ \underline{ \underline{ \: \: \: Explanation \: \: \: \: }}}$

First five multiples of 3 is 3 , 6 , 9 , 12 , 15

$\bold{Therefore \: , \: }$

$\to$ First Term ( a )= 3

$\to$ Last Term ( l ) = 15

$\to$ Number of Terms ( n ) = 5

$\bold{ \underline { We \: know \: that \: , \: </p><p> \: }}$

$\fbox{ \fbox{ \large{ \bold{Sum \: = \: \frac{n}{2} \: ( \: a + last \: term\: )}}}}$

$\bold{ \to \: Sum = \frac{5}{2} \: ( \: 3 + 15 \: )} \\ \\ \bold{ \to Sum = \frac{5}{2} \times (18)} \\ \\ \bold{ \to Sum = \frac{90}{2} } \\ \\ \bold{ \to Sum = 45 }$