Question
A bag contains red, blue, and green balls in the ratio
of 2:4:5. If two balls are randomly selected from the bag, the probability that both are blue is 1/8 . Determine the total number of balls in the bag.Solution
Let the number of red, blue and green balls in the bag are 2x, 4x and 5x respectively. Total number of balls in the bag = 2x + 4x + 5x = 11x So according to question: 4xC2/11xC2 = 1/8 4x (4x – 1)/ 11x (11x – 1) = 1/8 (16x – 4)/ (121x – 11) = 1/8 128x – 32 = 121x – 11 7x = 21, x = 3 So the total number of balls in the bag = 33
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