Question

find the sum of all three digits number which are divisible by 9​

Answer 1

≡QUESTION≡

Find the sum of all three digits number which are divisible by 9.

                                                                                               

║⊕ANSWER⊕║​

The 3 digit no:s divisible by 9 ARE :

108, 117 ,126....... ,999.

First term = a

                = 108

Common difference = d = 9

last term = aₙ = 999

no: of terms  = n = ?

aₙ=A+(n-1)d

999 = 108 +(n - 1)9

891 = 9n - 9

900 = 9n

n = 900/9 = 100

Sₙ = n/2 ( a + aₙ)

     = 100/2 ( 108 + 999)

     = 50 * 1107

     = 55350

∴Sum of all the 3 digits numbers which are divisible by 9 = 55350