Question
There are 30 cars standing in a parking lot which
consist of silver, grey and white cars. The number of grey and white cars are equal, and the number of silver cars is 3 more than the number of white cars. If 3 cars are randomly selected, what is the probability that at least one of them is silver?Solution
Let the number of grey and white cars be ’x’ each. Then the number of silver cars will be ‘x + 3’. So, (x + 3) + x + x = 30 3x = 27 x = 9 So, number of silver, grey and white cars is 12, 9 and 9 respectively. Required probability = P (at least one of them is silver) = 1 – P (none of them is silver) = 1 – (18/30) × (17/29) × (16/28) = 1 – (204/1595) = (1391/1595)
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