Question

in an ap the first terms is 8 , nth terms is 33 and sum of first n term is 123, then find the value of n

Answer 1

Its so easy, use formula sn = n/2 [ a + an ]
123 = n/2 [ 8 + 33 ] 
123*2 = n ( 41 )
123*2/41 = n
root 36 = n
6 = n
:D

Answer 2

your. answer is here

hope it help