Question

the sum of certain numbers of terms in ap is 5500.if the first and the last terms are 100 and 1000 respectively, find the number of terms

Answer 1

Answer:

200

Step-by-step explanation:

S

14

=1050

a=10

S

n

=

2

n

[2a+(n−1)d]

1050=

2

14

[2×10+(14−1)d]

7

1050

=[20+14d−d]

150−20=13d

130=13d

d=10

The 20

th

term is

a

20

=a+(n−1)d

=10+(20−1)10

⇒10+190

a

20

⇒200