My Primary 3 student was asking how to do this:-
1+2+3+4......................+97+98+99+100 = ?
we need to add the numbers from both ends, 2 at a time. For example, the 1st number "1" and last number "100" adds up to "101". The 2nd number "2" and last 2nd number "99" adds up to "101" also. If you keep doing this, all the numbers will add up to "101".
From 1- 100, there is 50 sets of 2 numbers-----> 100/2=50
Each set gives you a sum of 101.
Hence total would be 101 x 50 = 5050 (Ans)
