Question

the vlaue of : 1+3+5+7+.......+25 is? ​

Answer 1

Answer:

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Step-by-step explanation:

We take the first term =a=1, last term =l=25, common difference =d=2 and the number of terms =n.

Then, since it is an A.P. series,

n=  

d

l−a

​  

+1

=  

2

25−1

​  

+1

=13.

Let S  

n

​  

 be the sum of n=13 terms

∴S  

n

​  

=  

2

n

​  

×(a+l)

=  

2

13

​  

×(25+1)

=13×13=169.

So the required sum =169