Question

Find the common difference of an AP whose 1st term is 4, last term is -49 and the sum of all term 265.

Answer 1

a=4 , last term is -49 and sum is 265
to find : common difference .
by formula , s = n/2 ( a+ l)
265*2 = n (-45)
so n = 265*2/-45
now l= a + (n-1)d
-49 = 4 + ( -530/45 -1 ) d
-53 =( -530-45/45)d
-53*45/-575 = d
d = 4.14 (approx .)
hope it helps .....