Problem 638

Find S25 for \frac{1}{2}+1+\frac{3}{2}+2+...

 

Solution:-

 

We know S =  \frac{n}{2}[2a_{1}+(n-1)d] , Where a1 = first term , n = finding term , d = second term – first term

S25 =  \frac{25}{2}[2*(\frac{1}{2})+(25-1)(\frac{1}{2})]

S25 = \frac{325}{2}

So the value of S25   \frac{325}{2}

 

 

 

 

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