Question

Find the sum of the even integers between 30 and 70

Answer 1

SUM OF INTEGERS BETWEEN 30 AND 70 (excluding 30 and 70)

the even nos. go on like 32 , 34, 36..... 68

first even no. = 32

last even no. = 68

Use an = a + (n-1)d : d is common difference = 2

68 = 32 + (n-1)*2

18 = n - 1

n = 19

now us sum of A.P. formula

S = (n/2)(a + an) = (19/2) (68+32) = 950