FINDING PROBABILITY WORKSHEET

Problem 1 :

What is the probability of rolling an even number on a standard number cube ?

Problem 2 :

What is the probability picking a purple marble from a jar with 10 green and 10 purple marbles.

Problem 3 :

What is the probability of rolling a number greater than 4 on a standard number cube ?

Detailed Answer Key

Problem 1 :

What is the probability of rolling an even number on a standard number cube ?

Solution : 

Step 1 :

Find the sample space for a standard number cube.

There are 6 possible outcomes.

S  =  {1, 2, 3, 4, 5, 6}

Step 2 :

Find the number of ways to roll an even number.

The event can occur 3 ways.

{2, 4, 6}

Step 3 :

Find the probability of rolling an even number.

Substitute values and simplify.

P(even)  =  3/6

P(even)  =  1/2

The probability of rolling an even number is 1/2.

Problem 2 :

What is the probability picking a purple marble from a jar with 10 green and 10 purple marbles.

Solution : 

Step 1 :

Find the sample space for a standard number cube.

There are 20 possible outcomes.

10 Green marbles and 10 Purple marbles 

Step 2 :

Find the number of ways to pick a purple marble.

The event can occur in 10 ways.

Because we have ten purple marbles. 

Step 3 :

Find the probability of picking a purple marble. 

P (purple)  =  No. of purple marbles / Total no. of marbles

Substitute values and simplify.

P (purple)  =  10 / 20

P (purple)  =  1/2

The probability of picking a purple marble is 1/2.

Problem 3 :

What is the probability of rolling a number greater than 4 on a standard number cube ?

Solution : 

Step 1 :

Find the sample space for a standard number cube.

There are 6 possible outcomes.

S  =  {1, 2, 3, 4, 5, 6}

Step 2 :

Find the number of ways to roll a number greater than 4.

The event can occur 2 ways.

 {5, 6}

Step 3 :

Find the probability of rolling a number greater than 4.

P ( > 4 ) =  No. of numbers > 4 / Total no. of numbers

Substitute values and simplify.

P ( > 4 )  =  2 / 6

P ( > 4 )  =  1/3

The probability of rolling a number greater than 4 is 1/3.

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