Question

How many terms of A.P 8,13,18,23......... must must be taken to give the sum of 1110​

Answer 1

Given:

A.P 8,13,18,23.........

To find:

How many terms of A.P 8,13,18,23......... must must be taken to give the sum of 1110​

Solution:

From given, we have,

A.P series 8, 13, 18, 23, .........

The first term, a = 8

The common difference, d =  13 - 8 = 5

The formula for calculating the sum of terms of the series AP is

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

1110 = n/2 [8 + (n - 1) 5]

2220 = n [8 + 5n - 5]

2220 = n [3 + 5n]

2220 = 3n + 5n²

5n² + 3n - 2220 = 0

Now solve this quadratic equation to obtain the value of n

So, we have,

n = -3/10 ± √44409/10

Hence 1110 cannot be the sum of given AP series