Question

Find the sum of first 15 terms of an AP whose 4th and 9th terms are -15 and -30 respectively.

Answer 1

Answer:

ANSWER

a=1,l=11,S

n

=36

S

n

=

2

n

(a+l)

36=

2

n

(1+11)

⇒36=

2

n

×12

⇒36=6n

⇒n=6

Hence, option (B) is correct.

Step-by-step explanation:

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