Question

Find the sum of all natural numbers between
1 and 145 which are divisible by 4.​

Answer 1

Answer:

All natural numbers bwetween 1 and 145 which are divisible by 4 are,

4,8,12,16,...,144 forms an A.P

with a=4 and d=4

Let, t

n

=144

⟹a+(n−1)d=144

⟹4+(n−1)4=144

⟹4(n−1)=140

⟹n−1=35

∴n=36

Now, S

n

=

2

n

[a+l]

=

2

36

[4+144]

=18×148

=2664