pkw209 wrote:Hey all,
Could figure this one out. A brief explanation would be much appreciated. Thanks!
A basket has 5 apples, one is spoiled. If Henry picked 2 apples simultaneously and at random, what is probability that the 2 selected apples will include the spoiled one.
a. 1�5
b. 2�10
c. 2�5
d. 1�2
e. 3�5
Using my 5-step method for probability:
1) Lay out the number of events (here, we have 2 events):
_ _
2) Label each event with one specific example of the desired outcome:
_ _
S NS
(NOTE: S = spoiled, NS = not spoiled)
3) Label each event with its relevant probability and multiply across (here, we have a selection of elements where elements are removed), known as the "specific probability"
1/5 1 = 1/5
S NS
(NOTE: Since only non-spoiled remains for the second selection, the probability of selecting a non-spoiled is 100%)
4) Determine the number of ways in which the desired event can be presented (here, we have 2 ways):
S NS
NS S
5) Multiply the result of step 3 by the result of step 4:
1/5 x 2 = 2/5
(NOTE: When the specific probability is different for each possibility (which can occur), add the specific probabilities together).
(NOTE: I have noticed some comments about the accuracy of some math problems. I completely agree that GMAT students should be 100% that they have accurately re-created the question. Since the GMAT uses all the information in the questions, any mistake or omission can cause real problems. I once couldn't solve an exponent question that a student provided because the student listed the exponent as "8" instead of "18". Once it was changed to "18", the problem flowed easily).
