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A certain box has 10 cards written integers from 1 to 10 inclusive and the numbers written are different. If 2 different cards are selected at random, what is the probability that the sum of the numbers written on the 2 cards selected less than the average (arithmetic mean) of total 10 numbers written on the 10 cards?
A. 2/45
B. 1/15
C. 4/45
D. 1/9
E. 2/15
The OA is C.
Average of 10 cards = (1 + 10)/2 = 5.5
Number of ways of picking 2 cards from 10 cards = 10C2 = 45
Possible ways of picking 2 cards such that sum will be less than 5.5 = (1 + 2), (1 + 3), (1 + 4), (2 + 3) = 4
Probability = 4/45
Has anyone another strategic approach to solve this PS question? Thanks!
A. 2/45
B. 1/15
C. 4/45
D. 1/9
E. 2/15
The OA is C.
Average of 10 cards = (1 + 10)/2 = 5.5
Number of ways of picking 2 cards from 10 cards = 10C2 = 45
Possible ways of picking 2 cards such that sum will be less than 5.5 = (1 + 2), (1 + 3), (1 + 4), (2 + 3) = 4
Probability = 4/45
Has anyone another strategic approach to solve this PS question? Thanks!
