Question

The 12th term of an Ap series is (-13).the sum of first 4 terms is 24.find the sum of the first ten terms.
will mark brainliest!

Answer 1

Answer:

sum of first 10 terms is "0"

Answer 2

Answer:

The sum of first 10 terms is 0.

Given:

The 12th term of an AP series is (-13).

The sum of first 4 terms is 24.

To find:

The sum of the first ten terms.

Solution:  

In an AP, $t_{n}$ = a + (n-1) d

Where,

a is the first term,

n is the position of the term,

d is the common difference.

$t_{12}$ = a + (12-1) d

-13 = a + 11d …... (1)

Sum of 1st four terms,  a , a + d, a+ 2d, a + 3d

4a + 6d = 24

2a + 3d = 12 ….. (2)

Solving (1) and (2), we get a = 9, d = -2

Sum of 10 terms,

$s_{n} = \frac{n}{2}$ (2 a + (n-1) d)

$s_{10} = \frac{10}{2}$} ( 2 (9) + (10-1) -2)

$s_{10}$=5 (18 – 18)

$s_{10}$  = 0.

Result:

The sum of the first ten terms is 0.