Question

Find the sum of all numbers from 50 to 350 which are divisible by 6 .Hence find the 15th term of an A.P.

Answer 1

the numbers divisible by 6 are

54, 60, ........... 348

$n = \frac{l - a}{d} + 1$
$= \frac{348 - 54}{6} + 1$
$= 50$
$sum = \frac{n}{2} (a + l)$
$= 25 \times 402$
$= 10050$
$15th \: term \: = a + (n - 1)d$
$= 54 + (14 \times 6)$
$= 138$

Answer 2

I hope u have understood this answer