Sum of even numbers:-

[NishantG]

Absolutely agree that the value of n should be 159

Error done by retake and others is that number of even numbers in the series should be (n-1)/2 and not n

So if you substitute this value in formula

Sum of AP = n/2(2*1st number + (n-1)d)

Here n=(n-1)/2 and d= 2

So sum of even numbers between 1 to n is (n-1)(n+1)/4

Using this formula value of n is 159

[gmatcraze]

Can someone explain the solution to this problem again .....Sorry, can't understand the solutions given ...

[manikdhingra]

we have a formula for the sum of first n even no.s as n(n+1).....by which we can deduce that n=79