Addition of Numbers in Sequence

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)

Back after 2 years...

Hihi,

time passes and my kids are now both 4 years and 2 years old respectively. These 2 years have been fruitful, my kids grew up, we started KEN Tuition Centre at 256 Yishun Ring Rd, and we shifted house from Sembawang to Yishun. I hope to have the time to add more to this blog from now on.

Rgds,
Kenny Wong.