Probability Worksheets
Free printable probability worksheets: find the chance of an event on a spinner, in a bag of counters or on two spinners, as a fraction. With an answer key.
Each problem draws a spinner, a bag of counters or a pair of spinners, and asks for the probability of an event: how likely it is, as a fraction. A spinner is cut into equal sections with a number in each, so the student counts sections and never judges an angle. The counters in a bag each carry a letter, with a key under the bag, so the sheet still reads in black and white.
A probability is the number of ways the event can happen over the number of equally likely outcomes. On a spinner with six sections, three of them even, the probability of an even number is 3/6, which is 1/2 in lowest terms. Every sheet says to write each answer in lowest terms, and many of the questions are chosen so that the first fraction a student finds needs simplifying. An event that cannot happen has a probability of 0, and one that must happen has a probability of 1.
Each sheet deals the three kinds of question evenly: one spinner, a bag of counters and two spinners. The numbers on a spinner are 1 to 9 and can repeat, which is how one number comes to be likelier than another. A bag holds between 5 and 12 counters. Some of the two-spinner questions ask only how many different outcomes there are, and the answer to those is a whole number.
What this worksheet covers
- Find the probability of an event on a spinner
- Find the probability of drawing a colour from a bag of counters
- Write a probability as a fraction in lowest terms
Common Core standards
- 7.SP.C.5 Understand that the probability of an event is a number from 0 to 1 that expresses how likely it is to occur.
- 7.SP.C.7a Develop a uniform probability model and use it to find the probabilities of events.
- 7.SP.C.8b Represent sample spaces for compound events and identify the outcomes that make up an event.
Frequently asked questions
How do you find the probability of an event?
Count the outcomes where the event happens and divide by the number of equally likely outcomes. A spinner with 8 equal sections, 3 of them marked 5, gives a probability of 3/8 of spinning a 5.
What does lowest terms mean for a probability?
The top and bottom of the fraction have no common factor left. On a spinner with 6 equal sections, 4 of them even, the probability of an even number is 4/6. Dividing both numbers by 2 gives 2/3, which is the answer in lowest terms.
Can a probability be 0 or 1?
Yes, and they are the two ends of the scale. An event that cannot happen has a probability of 0: on a spinner marked with the numbers 1 to 4, spinning a 7. An event that must happen has a probability of 1: spinning a number less than 10. Every other event falls between them.
Why do the counters in the bag have letters on them?
These sheets print in black and white, where colours cannot be told apart, so each counter carries a letter and the key under the bag says which colour each letter stands for. The probability then comes from counting letters. In a bag with 3 R, 2 B and 1 G, the probability of taking an R is 3/6, which is 1/2.