SOLUTION: jar contains 110 marbles of which 50 are red and 60 are green. The probability of picking a red marble from the jar without looking is, therefore, 50/110. How many red marbles mu

Question 307073: jar contains 110 marbles of which 50 are red and 60 are green. The probability of picking a red marble from the jar without looking is, therefore, 50/110. How many red marbles must be added to the jar so that the probability of picking a red marble will be 2/3?
Answer by rapaljer(4671) (Show Source): You can put this solution on YOUR website!
If you add x red marbles to the jar, then there will be
50+x red marbles, and 110 + x total marbles. If the final probability is to be 2/3, then solve this equation:

Since means that ,
means that

Subtract 2x from each side:

Subtract 150 from each side:

Check: You now have 50+70=120 red marbles, and 110 + 70= 180 total marbles.
The probability of getting a red marble is .

Dr. Robert J. Rapalje, Retired
Seminole State College of Florida
Altamonte Springs Campus
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