This is an Arithmetic Progression with common difference of -2.
Now using the sum of first n terms we get.
(2a+(n-1)d)=250
Here a=148 and d=-2
So we have
(296-2(n-1))=250
2(n-1)=46
n-1=23
n=24
This is the Required Value of n;
Here we have used the formula for the sum of AP.
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