Question

The sum of the first 16 term of an Ap is 240 and the sum of the next 4 term is 220 find the common different, find the first term and find the sixteeth term

Answer 1

Answer:

Sum of first n terms of an AP is given as

S=

2

n

[2a+(n−1)d]

n=20,S=−240,a=7

⇒−240=

2

20

[2×7+(20−1)d]

⇒−240=10[14+19d]

⇒−240=140+190d

⇒−190d=140+240

⇒−190d=380

⇒d=

−190

380

=−2

n

th

term of an AP =a

n

=a+(n−1)d

⇒a 24

=7+(24−1)(−2)

⇒a 24

=7−46

⇒a 24

=−39