Unit E: Statistics and Probability

Chapter 2: Probability

Practice


Instructions: Click the Download File button to download a printable PDF of the questions. Answer each of the following practice questions on a separate piece of paper. Step by step solutions are provided under the Solutions tab. You will learn the material more thoroughly if you complete the questions before checking the answers.
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  1. A jewellery box contains 3 white pearls, 4 gold rings and 7 silver rings.

    1. What are the odds of choosing a white pearl from the jewellery box?
    2. What are the odds against choosing a gold ring?
    3. What is the probability of choosing a silver ring? Express the answer as a ratio.

  2. A gumball machine is filled with 5 yellow, 3 red, 9 orange and 10 blue gumballs. State the odds of choosing the following.

    1. a red gumball
    2. a gumball that is not blue
    3. a yellow or red gumball
       
A jewellery box contains 3 white pearls, 4 gold rings and 7 silver rings.

  1. What are the odds of choosing a white pearl from the jewellery box?
  2. What are the odds against choosing a gold ring?
  3. What is the probability of choosing a silver ring? Express the answer as a ratio. 


  1. favourable outcomes (white pearl)
    		3
    unfavourable outcomes (not a white pearl)
    		11


    odds   in   favour = number   of   pearls   :   number   of   items   that   are   not   pearls = 3 : 11

    The odds in favour of choosing a white pearl are 3:11.

  2. favourable outcomes (gold ring)
    		4
    unfavourable outcomes (not a gold ring)
    		10


    odds   against = number   of   gold   rings   :   number   of   items   that   are   not   gold   rings = 10 : 4 = 5 : 2

    The odds against choosing a gold ring are 5:2.

  3. probability = number   of   silver   rings total   number   of   items = 7 14 = 1 2

    The probability of choosing a silver ring is 1:2.
A gumball machine is filled with 5 yellow, 3 red, 9 orange and 10 blue gumballs. State the odds of choosing the following.

  1. a red gumball
  2. a gumball that is not blue
  3. a yellow or red gumball


  1. favourable outcomes (red gumball)
    		3
    unfavourable outcomes (not a red gumball)
    		24


    odds   in   favour = number   of   red   gumballs   :   number   of   gumballs   that   are   not   red = 3 : 24 = 1 : 8

    The odds of choosing a red gumball are 1:8.

  2. The odds of choosing a gumball that is not blue are the same as the odds against choosing a blue gumball.

    favourable outcomes (blue gumball)
    		10
    unfavourable outcomes (not a blue gumball)
    		17


    odds   against = number   of   gumballs   that   are   not   blue   :   number   of   blue   gumballs = 17 : 10

    The odds against choosing a blue gumball are 17:10. Therefore, the odds of choosing a gumball that is not blue are 17:10.

  3. favourable outcomes (yellow or red gumball)
    		5 + 3 = 8
    unfavourable outcomes (not a yellow or red gumball)
    		19


    odds   in   favour = number   of   yellow   or   red   gumballs   :   number   of   gumballs   that   are   not   yellow   or   red = 8 : 19

    The odds of choosing a red or yellow gumball are 8:19.