Gmat_mission wrote: ↑Sun Jun 07, 2020 4:11 am
Gambling with 4 dice, what is the probability of getting an even sum?
A. 3/4
B. 1/2
C. 2/3
D. 1/4
E. 1/3
[spoiler]OA=B[/spoiler]
Solution:
Since the sum of the 4 numbers on the dice is either odd or even, we can use the formula:
P(even sum) = 1 - P(odd sum)
To get an odd sum, the 4 numbers on the dice must be 3 odd and 1 even OR 1 odd and 3 even.
P(3 odd and 1 even) = 1/2 x 1/2 x 1/2 x 1/2 x 4C3 = 1/16 x 4 = 1/4
P(1 odd and 3 even) = 1/2 x 1/2 x 1/2 x 1/2 x 4C1 = 1/16 x 4 = 1/4
So, P(odd sum) = 1/4 + 1/4 = 1/2 and therefore, P(even sum) = 1 - 1/2 = 1/2.
Answer: B
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