Question

If 12th term of an A.P is -13 &the sum of its first 4 terms is 24 what is the sum of its first 10 terms?

Answer 1

the sum of the first 10 terms of the ap is 0

Answer 2

Hii friend,

12th term of an AP = -13

a+11d = -13......(1)

And,

Sum of first fourth term = 24

N/2× [ 2A + (N-1) × D)] = 24


4/2× [ 2A + (4-1) × D] = 24

2 ×(2A + 3D) = 24

4A+ 6D = 24......(2)

From equation (1) we get,

A + 11D = -13

A = -13-11D......(3)

Putting the value of A in equation (2)

4A + 6D = 24

4 × (-13-11D)+ 6D = 24

-52 - 44D +6D = 24

-38D = 24+52

D = 76/-38 = -2

Putting the value of D in equation (3)

A = -13-11D => -13 - 11 × -2 => -13 +22 => 9

First term (A) = 9

Therefore,

Sum of first 10th term = N/2 × [2A + (N-1) × D]

S10 = 10/2 ×[ 2 × 9 + (10-1) × -2)]

=> 5 ×(18 -18)

=> 0



HOPE IT WILL HELP YOU..... :-)