Grade 8 · Math

8th grade Chance of "this or that": overlapping and mutually exclusive events worksheet

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Chance of "this or that": overlapping and mutually exclusive events

Grade 8 Math Worksheet - Challenge Me

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Circle the best answer, or write your answer on the line.

In Ari's class of 30, 12 students play soccer, 10 play piano and 4 do both. In simplest form, what is the chance a student picked at random plays soccer or piano?
Of 40 families on Esme's street, 15 have a cat, 20 a dog and 5 both. In simplest form, what is the chance a family picked at random has a cat or a dog?
3.
Jun picks one card at random from cards 1 to 10. What is the chance of an even number or a number over 6?
- 9/10
- 1/5
- 7/10
4.
For Kira's events, P(A) = 0.5, P(B) = 0.4 and P(A and B) = 0.1. What is P(A or B)?
- 0.2
- 0.9
- 0.8
5.
Why does Luz subtract the overlap when finding P(A or B)?
- They were counted in both groups
- They cannot happen on one try
- Subtracting keeps the chance below 1/2
6.
Milo says P(even or a 2) on a fair number cube is 1/2 + 1/6 = 2/3. Agree or disagree?
- Disagree: 2 is even, so it is 1/2
- Agree: add the chances of the two events
- Disagree: multiply to get 1/12
7.
Noah says P(A or B) = 0.7 + 0.6 = 1.3. Agree or disagree?
- Agree: likely events add to 1.3
- Disagree: a chance is at most 1
- Agree: 1.3 means very likely
8.
Pia says 'rolling a 2' and 'rolling a 5' cannot happen on one roll. Agree or disagree?
- Disagree: their chances are equal
- Disagree: a cube shows both numbers
- Agree: one roll shows one number
9.
Of Tala's 20 classmates, 8 do art, 6 do drama and 2 do both. What is the chance one does neither?
- 2/5
- 3/10
- 3/5
10.
For Zee's events, P(A or B) = 0.65. What is the chance of neither A nor B?
- 1.65
- 0.65
- 0.35

8th grade Chance of "this or that": overlapping and mutually exclusive events worksheet – printable — Print: 1 2 3 4 5 6

About this worksheet

Find the chance of an event, its opposite, and 'this or that' for events that do or do not overlap. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

I can find the chance an event does NOT happen as 1 minus its chance.
I can tell whether two events can happen on the same try.
I can add the chances of two events that cannot happen together.
I can find the chance of A or B for overlapping events by taking the overlap away once.

Standard: IXL parity (Nov 11) (nearest: 7.SP.C.8; S-CP.B.7 in Algebra 2)

Words to know

outcome: One possible result, like rolling a 4

event: A set of outcomes, like rolling an even number

opposite (complement): Every outcome the event leaves out

cannot happen together (mutually exclusive): Two events that share no outcome

overlap: Outcomes that are in both events

Common mistakes

Your child gave the chance of the event itself. The question asked for the opposite, so take the event's chance away from 1.

Your child multiplied the two chances. Multiplying is for 'this and then that'; for one pick that is 'this or that', add the chances.

Your child added the two groups but counted the outcomes in both groups twice. Add the groups, then take the overlap away once.

Questions parents ask

What is the most common mistake with chance of "this or that": overlapping and mutually exclusive events?

Your child gave the chance of the event itself. The question asked for the opposite, so take the event's chance away from 1.

Are these 8th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

More grade 8 math

See all grade 8 math

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