A shooter firing at a target has 10% chance of hitting the target in one shot. The number of times he must fire at the target to have above 50% chance of hitting the target is

A. 11

B. 9

C. 7

D. 5

Solution(By Examveda Team)

Required Probability,
1/10+ 9/10*1/10 + (9/10)² *1/10 + ................ + (9/10)ⁿ *1/10 > 50%.
1/10+ 9/10*1/10 + (9/10)² *1/10 + ................ + (9/10)ⁿ *1/10 > 1/2
It gives geometric series so we have on solving with GP help.
(9/10)ⁿ > 1/2
Now for n = 7
Probability would be more than 50%.