Question

If 13th term of an AP is four times its 3rd and 5th term is 16. Find sum of its first 10 terms.

please do answer this question ASAP !!

Answer 1

T5 = 16

=> a + 4d = 16 ------(1)

T13 = 4 × T3

=> a + 12d = 4( a + 2d)

=> a + 12d = 4a + 8d

=> a - 4a + 12d - 8d = 0

=> 4d - 3a = 0

=> 3a - 4d = 0 -------(2)

On adding equation 1 and 2, we get

4a = 16

=> a = 4

Now,

On putting the value of a in equation 1, we get

4 + 4d = 16

=> 4d = 12

=> d = 3

S10 = 10 /2 [ 2(4) + (10-1)(3)]

= 5 ( 8 + 27)

= 5 × 35

= 175

Answer 2

Refers to attachment ♡~~