Question

The sum of the first 7 terms of an AP is 63 and the sum of its next 7 terms is 161.Find the 28th

term of this AP​

Answer 1

Answer:

Here,

S7=63 S14=161

a+6d=63.... (i) a+13d=161...... (ii)

Subtracting eq. (i) from eq. (ii) we get,

a+13d-a-6d=161-63

7d=98

d=14

Putting the value d=14 in eq. (i) we get,

a+6×14=63

a=63-84

a=(-21)

Therefore,

the a28 = a+27d

= -21+27×14

=-21+378

=357