Question

first term last term and common difference of AP is 17,350 and 9 respectively find the sum of nterms is​

Answer 1

a = 17

d = 9 ,

l = 350                          { ∴ l represents last term }

∵ a + ( n - 1 ) d = l

17 + ( n - 1 ) 9 = 350

( n - 1 ) 9 = 350 - 17

( n - 1 ) 9 = 333

n - 1 = 333 / 9

n - 1 = 37

n = 37 + 1

n = 38

∵ Sn = n /2 ( a + l )

S₃₈ = 38 / 2 ( 17 + 350 )

S₃₈ = 19 × 367

S₃₈ = 6973