Question

In an ap if the 12th term is -13 and the sum of 1st 4 terms is 24. Whats is the sum of first 10 terms?

Answer 1

InA.p,12th term=-13

a+11d=-13•••••••••(1)

a-first term,d-common difference

sumof first n terms inA.p=n/2 (2a+(n-1)d)

sum of 1st four terms=4/2 (2a+3d)=24

2a+3d=12•••••••••••(2)

solving(1)&(2)

a=9,d=-2

sum of frist 10 terms=10/2 (2×9+9 (-2))

.. =0