There are 5 switches in a board. In these 5 switches 1 is attached with the fan. A person has to sta

M4maths Previous Puzzles

14 Oct 2011 board

There are 5 switches in a board. In these 5 switches 1 is attached with the fan. A person has to start the fan in 2 attempts only. Probability of success will be

OPtion

1) 1/5
2) 2/5
3) 3/5
4) 4/5
5) 1
6) 1/2
7) 1/3
8) 1/4
9) 2/3
10) none of these

Solution

Probability of success in first attempt = 1/5
Probability of success in second attempt after first unsuccessful attempt = (4/5)*(1/4) = 1/5
so total probability = 1/5 + 1/5 = 2/5

Correct Option: 2 Best Solution (6)