The probability that a coin is in the [math]i[/math]th box is [math]1/(i+1)[/math]. If you search in the [math]i[/math]th box and it is there, you find it with probability [math]i/(1+i)[/math]. Determine the probability that the coin is in second box, given that you have looked in the fourth box and not found it.

• 0.35
• 0.4
• 0.45
• 0.5
• 0.55

References

Doyle, Peter G. (2006). "Grinstead and Snell's Introduction to Probability" (PDF). Retrieved June 6, 2024.