Question

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

Answer 1

First term after 50 which is divisible by 6. 54 is first term. So, a=54 and d=6, n=15 because of 15th term.
T=a+(n-1)d
=54 +(15-1)6
=54 + 84
=138

Answer 2

The list of. number divisible by 6 between 50 to 350 are:54,60,.............348
Here-
a=54
an=348
d=6
thus,an=a+(n-1)d
348=54+(n-1)6
294/6=n-1
49+1=n
# n=50


Therefore;
S 50=n/2(a+an)
=50/2(54+348)
=25*402
=10050