A bag contains 5 black, 4 white and x red marbles. If the probability of picking a red marble is 2/5, find the value of x
- 8
- 10
- 4
-
6
The correct answer is: D
Explanation
Black = 5
White = 4
Red = x
Total = 9+x
P(red) = 2/5
x / (9+x) = 2/5
5x = 2(9+x)
5x = 18+2x
5x-2 = 18
3x = 18
x = 6