Question

In an AP
find d and a10

Answer 1

Hiii friend,

A3 = 15

a +2D = 15....(1)

S10 = 125

N/2 × [2A + (N-1) × D)] = 125

10/2 × [ 2A + (10-1) × D] = 125

5 × (2A + 9D) = 125

10A + 45D = 125.....(2)

From equation (1) we get,

a + 2D = 15

a = 15-2D.....(3)

Putting the value of A in equation (2)

10A + 45D = 125

10 × (15-2D) +45D = 125

150 -20D +45D = 125

25D = 125-150

D = -25/25 => -1

Putting the value of D in equation (3)

a = 15-2D => 15 - 2 ×-1 => 15+2 = 17


First term (A) = 17

And,

Common difference (D) = -1

therefore,

10th term of an AP = a+9d => 17 + 9 × -1 = 17-9 = 8.


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