Question

Find the sum of all 2digit natural numbers which is divisible by 4

Answer 1

Step-by-step explanation:

Hey Mate

Smallest Two digit number =10

Largest Two Digit Number=99

a=10

d=1

Last Term =99=an

an=a+(n-1)d

an=10+(n-1)1

99-10=n-1

n=90

Therefore Sum =Sn=n/2(a+L)

Sn=90/2[10+99]

Sn=45*109

Sn=1305

Answer 2

smallest 2 digit no. divisible by 4 =12

largest 2 digit no. divisible by 4 = 96

an= a+ (n-1)d

96 = 12+(n-1)4

84=4n-4

80=4n

n=20

Sn= n/2(a+an)

Sn=10(12+96)

=10(108)

=1080