## Melissa is painting the walls in study rooms at the library. She estimates that she will need 1/6 gallon of paint for each wall. How many walls can she paint with 6 gallons of paint?

October 14, 2019// Blog//

There are a few ways to look at this. If you wanted to look at all the events, you could draw a 6 x 6 grid and label the left side from 1 to 6 and the bottom from 1 to 6. The intersection of a row and a column would be a possible sum. You can check to see if the event you want to occur occurs on a cell by cell basis. Like if you wanted to see how many possibilities are there to get a sum of 12. We know there is only one way, that is to roll a 6 and a 6. Then you would shade the top right corner cell of the grid and check the other ones (for more complicated events). Then the probability is just the number of shaded cells divided by the total number of cells.

But, since you can probably just count the events, how many ways are there to roll any two numbers, if the order matters, there are 36 possibilities (6 x 6 grid). You could roll 4 then 6, 6 then 4, 5 then 5, 5 then 6, 6 then 5, and 6 then 6. There are 6 possibilities with a sum more than 9 and 36 total, so the probability of that one event is 6/36 or 1/6. Try out the last one 😉