Addition

Solution 1 : add the first and last term you will get 100, since there are 49 pairs and a 50 left in the middle, it is 100 * 49 + 50 = 4950

Solution 2 : use the formula n(n+1)/2 so it will be 99*100/2 = 4950

$\frac{(99)(100)}{2} = \boxed{4950}$

This is a arithmetic progression that have 1 as its first term (t1) and 99 as its n-th term (tn), with 99 terms (n). Hence, the asked sum will be the sum of the finite arithmetic progression as it follows and denoted by Sn: Sn=[(t1+tn) n]/2 => Sn=[(1+99) 99]/2 => :. Sn=4950.