For what positive integer \(n\) is \(\frac{1+2+3+\ldots + n}{2n} = 10\) true?
Thanks
-PharaoCarl
The numerator can be written as the sum
(n) (n + 1) / 2 so we have
(n)(n + 1)
________ = 10 simplify
2 * 2n
n + 1
_____ = 10 multiply both sides by 4
4
n + 1 = 40
n = 39
+53 
