Question

Find the sum of the first 10 multiples of 3.

Answer 1

Given: The first 10 multiples of 3 are 3, 6, 9, 12, 15, 18, 21, 24, 27, 30.

Step-wise calculation:

1. Write each term as 3 × n for n = 1..10:

Sum = 3(1 + 2 + 3 + ... + 10)

2. Compute the inner sum:

1 + 2 + ... + 10

= `10 xx 11/2`

= 55

3. Multiply:

3 × 55 = 165

The sum of the first 10 multiples of 3 is 165.