Question

Find the sum of all natural number from 50 to 250 which are divisible by 4.

Answer 1

52,56,60.....,148
Let a=52 and d=4 and l=148(l is the last term)
Tn =a+(n-1)d
148=52 +(n-1)4
148=52+4n-4
148=48+4n
4n=148-48
4n=100
n=100/4
n=25
Sn=n/2(a+l)
Sn=25/2(52+148)
Sn=25/2(200)
Sn=25(100)
Sn=2500