1 spoiled apple. 4 good apples. What is the probability that when two apples are picked, one is spoiled?
No. of ways of picking 2 objects from 5 objects is 5C2 = 10
Favourable situation is one spoiled apple and one good apple.
Do this in two steps. First pick a spoiled apple, and then a good one.
You can pick the spoiled apple in only 1 way.
AND You can pick the good apple in 4 ways
Thus there are 1*4 = 4 ways that one of the two picked apples is spoiled.
Probability = No. of Favourable outcomes / Total number of outcomes
= 4 / 10
= 2 / 5
I'm a GMAT newbie, and struggling with my introduction into ordering, combinations, etc. Could you elaborate a bit on the logic here? Thanks in advance.