Question

Find the sum of first 20 multiples of 6

Answer 1

The sum of 20 multiples of 6 is-
=>6+,12+,18+,24,+30,+36+,42+,48,+54+,60,+66,+72,+84,+90,+96,+102+,108,+114+,120.

Sum=1260

Answer 2

The first 20 multiples of 6 are 6,12,18,...,120
n=20,
a=6,
l=120

The sum of first 20 multiples of 6=

$sn = \frac{n}{2} (a + l) \\ = \frac{20}{2} (6 + 120) \\ = 10(126) \\ = 1260$

hope it helps u ^-^