A probability problem by A Former Brilliant Member
Probability
Level
2
There are 55 balls in a box. Some are colored green, blue and yellow. The probability of picking a green ball at random is 6/11. A boy added 20 yellow balls in the box. What is the new probability of picking a green ball at random?
3/5
2/5
1/5
4/5
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1 solution
Originally there are 30 green balls in the box (30/55=6/11). Then 20 yellow balls are added but there are still the same number of green balls, so the probability of picking a green ball is now 30/(55+20)=30/75=2/5