Question

The first and last terms of an A.Pare 1 and 11.if the sum of its terms is 36 , then the
number of terms is.............


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Answer 1

Given that, the first and last term of an AP 1 and 11.

and the sum of its terms is 36

Let, the number of terms be n and common difference be d.

We know, the formula of n

th

term of an A.P is

t

n

=a+(n−1)d

And, the formula of term n− terms of an A.P is,

S

n

=

2

n

[2a+(n−1)d]

By the question

t

n

→1+(n−1)d=11

⇒ d=

n−1

10

...(i)

S

n

→

2

n

[2.1+(n−1)d]=36

⇒ 2+(n−1)d=

n

72

⇒ d=

n(n−1)

72−2n

....(ii)

Comparing (i) and (ii) we get,

n(n−1)

10

=

n(n−1)

72−2n

⇒ 10n=72−2n

⇒ 12n=72

⇒ n=6

Hence, the number of terms is 6

hope it helps you dear

Answer 2

Explanation:

The first and last terms of an A.Pare 1 and 11.if the sum of its terms is 36 , then the

number of terms is.............

Don't spam otherwise I will be report your answer.

/