Question

Find the sum of all natural no:s less than 100 which are divisible by 6

Answer 1

Given :

• A.P : 6 , 12 , 18 , ........, 96

• First term ( a ) = 6

• Common difference ( d ) = 6

• Last term ( An ) = 96

To Find :

• Sum of all numbers given in A.P

Solution :

First we have to find no. of terms in this A.P

★ Aₙ = a + ( n - 1 ) d ★

⇒ 96 = 6 + ( n - 1 ) 6

⇒ 90 = ( n - 1 ) 6

⇒ n - 1 = 90/6

⇒ n = 15 + 1

⇒ n = 16

Now Sum of numbers in given A.P

★ Sₙ = n/2 ( a + l ) ★

⇒ S₁₆ = 16/2 ( 6 + 96 )

⇒ S₁₆ = 8 × 102

⇒ S₁₆ = 816

Answer 2

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