Let the total number of voters be 100V, then
Number of people who did not cast their vote = 10% of 100V = 10V
So, number of people who cast their votes = 100V – 10V = 90V
Rejected votes = 9V
Valid votes = 81V
Loss margin = 1V
The losing candidate got 40000 votes.
So, the winning candidate got 40000 + V votes.
So, 40000 + (40000 + V) = 81V
⇒ V = 1000
⇒ 100V = 100000
Hence, 100000 is the right answer.