+0  
 
0
34
2
avatar

A boy starts adding consecutive natural no.s starting from 1. After some time, ​he reaches a total sum of 1000 when he realises that he has double counted a number. Find the number double counted.

 Jun 26, 2020
 #1
avatar
+1

1000 x 2 = 2000

Sqrt(2000) =~45

[45 x 46] / 2 =1035

1035 - 1000 =35 - The number that was counted twice

 Jun 26, 2020
 #2
avatar+24609 
+1

\(\sum_{0}^{44}\) n =990

\(\sum_{0}^{45}\) n = 1035          HE MUST HAVE COUNTED '10'  TWICE !

 Jun 26, 2020

22 Online Users

avatar
avatar
avatar
avatar
avatar
avatar