Question

there was a scientist and one day his teacher asked him that add nukbers from 1 to 100 but he answered it in 30 secs. how he this and what is answer

Answer 1

S = 1+2+3+.............+99+100

And then, reversed the numbers to write
S = 100+99+........+3+2+1
when he added these two he got 2S as both the sums have to be equal.So he work,
2S = (100+1)+(99+2)...........+(3+98)+(2+99)+
(1+100)
= 101+101+101+.............+101+101 (100 times)
So, S = (100×101)/2 = 5050, I.e, the sum is 5050.

And that is scientist is "Gauss"