# Problem of the Day: 1/27/13

Gigahertz Car Rentals charges a daily fee plus a one-time expense. It costs \$132 to rent a car for two days and \$188 for three days. How much is the one-time expense?

Solution to yesterday’s problem:

Let’s use the blanks method to solve this problem, only this time we’ll fill in the blanks with probabilities instead of possibilities. Before, we used the blanks method to find out how many different ways there were to satisfy some conditions. This time, each blank represents Shruti drawing out one marble. The probability we put in each blank is the probability that the marble she draws is red. We need two blanks for two draws:

____ ____

On the first draw, there is an equal chance of drawing red or green (4/8 to draw red).

__1/2__ ____

On the second draw, there are only 7 marbles left. If the first draw satisfied the conditions, then only 3 of these are red.

__1/2__ __3/7__

We have to multiply these probabilities because we want the probability of both events occurring. The final answer is a probability of 3/14.