Maths-
General
Easy
Question
Number of Contestants by Score and Day
The same 20 contestants, on each of 3 days, answered 5 questions in order to win a prize. Each contestant received 1 point for each correct answer. The number of contestants receiving a given score on each day is shown in the table above.
No contestant received the same score on two different days. If a contestant is selected at random, what is the probability that the selected contestant received a score of 5 on Day 2 or Day 3, given that the contestant received a score of 5 on one of the three days?
The correct answer is: 0.714
HINT – Since selected contestant received the score 5 on one of the three days, it means that he is one of those candidates who received score 5 on all three days i.e. one of those 7 candidates
SOLUTION – We know that probability = 
Since no contestant received the same score on two different days , and selected contestant received the score 5 on one of the three days implies that
Probability = 
= 
So, probability that a selected contestant received score 5 on day 2 or
day 3 is 0.714
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