Question

7) How many terms of the arithmetic sequence {1,3,5, 7,...} will give a sum of 961?

n(2a1 + (n - 1)d)
Sn
2
-
You will need to factor to solve the quadratic equation

PLZ ANSWER

Answer 1

31 terms are required

Explanation:

a = 1

d = 3 - 1 = 2

Sum = (n/2) [ 2a + (n - 1)d ]

Let n terms are required:

=> 961 = (n/2) [2(1) + (n - 1)2]

=> 961 = (n/2) [2 + 2n - 2]

=> 961 = (n/2) [2n]

=> 961 = n²

=> √961 = n

=> ± 31 = n

As number of terms can't be -ve, n = 31