Mark the correct alternative in the following:
A rifleman is firing at a distant target and has only 10% chance o hitting it. The least number of rounds, he must fire in order to have more than 50% chance of hitting it at least once is
Given:
Chances of hitting a target in a trial=10%=
Chances of not hitting the target = 90%= 
Total probability = 50%=5
Let number of trials=n
So number of trials missed=n-1 to hit on nth trial
Total probability
= 5
Take log on both sides
n=6.58
n
7
So one must hit it seven times.
1