Theoretical Probability Practice

Find the probability of each event. Write your answer as a fraction, decimal, and percent.  Round to the nearest tenth of a percent.

  1. randomly choosing a white counter from a bag of 12 red counters, 12 white counters, 12 green counters, and 12 blue counters
  2. tossing two fair coins and having one land on tails and one land on heads [For this one, think about all the possible outcomes of two coin tosses. You could have both heads (HH), both tails (TT), head & tail (HT), or tail & head (TH). Of those 4 possible outcomes, what is the probability that one of the coins lands on heads and the other lands on tails?]
  3. rolling a number greater than 1 on a fair number cube
  4. randomly choosing an orange disk from a bag of 14 black disks, 4 blue disks and 12 orange disks
  5. randomly choosing 1 of the 6 R’s from a bag of 100 letter tiles
  6. spinning a number less than 7 on a fair spinner with 8 equal sections labeled 1–8

A set of cards has 20 cards with stars, 10 cards with squares, and 15 cards with circles. Find the probability of each event when a card is chosen at random.

  1. square
  2. circle
  3. star or circle
  4. not circle or square

 There are 14 girls and 18 boys in Ms. Wiley’s class. Ms. Wiley randomly selects one student to solve a problem. Find the probability of each event.

  1. selecting a boy
  2. selecting a girl