Question

Find the sum of 6+13+20+•••+97

Answer 1

Answer:

a = 6 , d = 13 - 6 = 7, an = 97

an = a + ( n - 1) d

97 = 6 + (n - 1) 7

7( n - 1) = 97 - 6

n - 1 = 91/ 7

n - 1 = 13

n = 14

there are 14 terms in the AP series

we want to find the sum of these no.

so, Sn = n/2 ( a + l)

Sn = 14/2 (6 + 97)

Sn = 7 × 103

Sn = 791 ..... Ans.

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