Question

10th term of an AP is 29 and it's 16th term exceeded its seventh term by 27. find sum of its 20 terms..

please give full calculation.

Answer 1

t10=29
t16=t7+27

then,

a+(10-1)d=29
a+(16-1)d=a+(7-1)d+27

now,
a+9d=29......1)
15d=6d+27..... 2)

from 2) we have:

9d=27
d=3

on putting value of d in eq1) we have:
a=2

t20=a+(20-1)d
2+19×3
=59



.hope it help____^_^__