GMAT Math Made Easy

Computing probability is simple, it is: SPECIFIC / TOTAL. What does it mean? Let's start with an example. Example . Suppose that you have a (six-sided) regular dice, whose sides contain numbers $1, 2, 3, 4, 5, 6$. If you throw the dice, the probability that you will get 6 can be computed as follows: TOTAL ($1, 2, 3, 4, 5, 6$) = $6$ sides; SPECIFIC (only $6$) = $1$ sides. Therefore, the probability that you get $6$ from throwing the dice once is equal to $1/6$.  Exercise . What is the probability that you get $3$ by throwing the same dice? Solution . TOTAL = $6$, as there are six sides for the dice, and SPECIFIC = $1$, because there is one side that has $3$. Thus, the probability that you get $3$ from throwing the dices once is equal to $1/6$. This is the answer. Let's spice up our example a little bit. Example . Suppose that you have two regular dices, each of which has six sides containing $1, 2, 3, 4, 5, 6$. If you throw both of them at once, wha