Question

If 12th term of an ap is -13 and the sum of its first four terms is 24 find the sum of its first ten terms

Answer 1

Answer:

0

Step-by-step explanation:

sum of first n terms in an ap is 0

Answer 2

The sum of first 10 terms is 0

Step-by-step explanation:

Formula of nth term of AP =$a_n=a+(n-1)d$

Substitute n = 12

So, $a_{12}=a+(12-1)d$

We are given that 12th term of an ap is -13

So, a+11d=-13

a=-13-11d

The sum of its first four terms is 24

Formula of sum of first n terms =$S_n=\frac{n}{2}(2a+(n-1)d)$

Substitute n = 4

So, $24=\frac{4}{2}(2a+(4-1)d)$

24=2(2a+3d)

12=2a+3d

Using 1

12=2(-13-11d)+3d

12=-26-22d+3d

12=-26-19d

38=-19d

-2=d

a=-13-11d

a=-13-11(-2)

a=9

Sum of first 10 terms = $S_{10}=\frac{10}{2}(2(9)+(10-1)(-2))=0$

Hence The sum of first 10 terms is 0

#Learn more:

The sum of first n terms of an AP is given by n²+8n. Find its 12th term?

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