GMAT Practice Question (One of Hundreds)
There are 7 "Nebraska" quarters, 6 "California" quarters, 4 "New Jersey" quarters, and 13 "Alabama" quarters in a sack. Karen is supposed to reach in and pick a quarter at random. She really wants a New Jersey quarter. What is the probability that she will get her wish?
Correct Answer: B
The probability of her wish coming true is the number of New Jersey quarters divided by the total number of quarters.
- There are 30 quarters in the sack (7+6+4+13).
- The probability that Karen gets her wish is P(New Jersey), which is (New Jersey Quarters)/(Total Quarters) = 4/30.
- Stated differently: There are 4 quarters, out of 30, that are New Jersey. So Karen has four possibilities of getting her wish.
- The fact she only gets to pick one quarter is not relevant. All that matters is what portion of the total number of quarters is the New Jersey version. So 4/30 quarters fit the bill. She also has 26/30 quarters that do not work. That means the correct response is 4/30, but you should reduce fractions when possible. That makes the correct response 2/15.
- Both C and D are large fractions not much less than 1. For either of those choices to be correct would mean she is almost certain to get her wished-for quarter. But logic should tell you the odds are slim. That leaves choices A and B.