The likelihood, or probability of an event occurring is always a number between 0 to 1. A 0 probability means something NEVER happens. A probability of 1 means it happens EVERY SINGLE TIME. 

All the probabilities between 0 and 1, now that's the tricky part, because now we've got to talk about parts of numbers. We have three ways we commonly express parts of numbers: fractions, decimals, and percents. All three are used interchangeably in probability, so make sure you check out the calculator video below to learn to CONVERT between these three forms of numbers. 

To determine the probability of an event occurring, simply make a ratio (ie a fraction) out of the number of "winning" events over the total number of possible events. Are the multiple choice answers in fraction form? Reduce your answer and you're done! Are they in decimal or percent form? Use your TI-30XS to convert to the desired form. 

Voila! I bet you wish all the math on the GED was this straightforward!

Here's an example: A bag contains 2 blue marbles, 3 red marbles, and 5 clear marbles. What is the likelihood that, if you reach into the bag and pull out one marble at random, you will draw a blue marble. 

There are 2 blue marbles. These are my "winners".

There are 10 total marbles. 

I'll make a ratio of "wins" to totals: 2/10.

Reduce for the answer in fraction form. Again, your calculator will do this for you! 1/5

Or convert to a decimal- 0.2- or percent- 20%. 

Watch the Virtual GED Class video below for a complete explanation and tons of worked example problems.