Quantitative Aptitude – Probability – A small store has five units of a new
XAT 2021 Exam Paper – Quantitative Aptitude – Probability – A small store has five units of a new
Q. A small store has five units of a new phone model in stock: two white, two black, and one red. Three customers arrive at the shop to buy a unit each. Each one has a predetermined choice of the colour and will not buy a unit of any other colour. All the three customers are equally likely to have chosen any of the three colours. What is the probability that the store will be able to satisfy all the three customers?
1/3
4/5
7/9
2/3
8/9
Answer: 2/3
Solutions:
Number of white phones = 2
Number of black phones = 2
Number of red phones = 1
customer 1 will have 3 choices
customer 2 will have 3 choices
customer 3 will have 3 choices
Hence total choices = 3 x 3 x 3 = 27
The cases not possible = BBB, RRR,WWW, RRB,RBR,BRR, RRW,RWR, WRR
Possible cases = 18
Probability = 18/27 = 2/3