GMAT Question of the Day – Problem Solving – Probability

Dan will go on vacation starting Monday morning. If on any day of his vacation Dan’s boss calls him, Dan must return to work that same evening. If on any given day there is a 20% chance that Dan’s boss will call him, what is the probability that Dan will return to work on Thursday evening?

A. .0896

B. .0872

C. .1012

D. .1024

E. .1128

[spoiler]D.[/spoiler]

GMAT Question of the Day Solution

In GMAT tutoring I’m always talking about staying organized. The people who I work with on GMAT are probably sick of me saying: “stay organized”. But hey – organization is the key to a great GMAT score. On probability questions it can help to make a map of what you are calculating before you put the actual numbers in. This can help you plan the question. You can see an example of a map in the attached diagram. Also – be smart with your arithmetic. Look for ways to simplify your calculations. You can see that the answers are in decimals so it will be smart to keep the denominators in powers of 10 so it is easy to calculate the decimal. You can also see that the numerator can be calculated in terms of powers of 2’s.