Calculating Simple Probability

Show your work for each problem.

1.
A bag contains 3 red marbles and 7 blue marbles. What is the probability of drawing a red marble?
1. a)
2. b)
3. c)
4. d)
Answer:
Total marbles = . Favorable outcomes (red) = . So .
2.
A spinner has 5 equal sections. What is the probability of landing on any one specific section? (Answer as a decimal)
Answer: 0.2
or . Each section has an equal chance of being selected.
3.
What is the probability of rolling a number less than on a standard die?
1. a)
2. b)
3. c)
4. d)
Answer:
Numbers less than 3: = 2 outcomes. Total outcomes = 6. .
4.
A deck of cards has 52 cards. What is the probability of drawing a King?
Answer: 1/13
1. How many Kings are in a standard deck? 4
2. How many cards total in the deck? 52
3. Write the probability as a fraction: Kings/Total 4/52
4. Simplify the fraction (divide both by 4) 1/13
5.
A bag has 8 equally likely outcomes. What is the probability of getting one specific outcome? (Answer as a simplified fraction like 1/8)
Answer: 1/8
With 8 equally likely outcomes, each has probability .
6.
A box contains 5 green balls, 3 yellow balls, and 2 purple balls. What is the probability of NOT drawing a green ball?
1. a)
2. b)
3. c)
4. d)
Answer:
Total = . Not green = . .
7.
A spinner has 12 equal sections numbered 1-12. What is the probability of landing on a multiple of 3?
Answer: 1/3
1. List all multiples of 3 from 1 to 12 3, 6, 9, 12
2. How many multiples of 3 did you find? 4
3. How many total sections on the spinner? 12
4. Write the simplified probability 1/3
8.
In a class of 25 students, 10 play soccer and 8 play basketball. If a student is chosen randomly, what is the probability they play soccer? (Answer as percentage, numbers only)
Answer: 40
. The basketball info is not needed!
9.
A jar contains 6 red candies, 4 blue candies, and 2 green candies. What is the probability of picking a red OR blue candy?
Answer: 5/6
1. How many red candies? 6
2. How many blue candies? 4
3. How many favorable outcomes (red OR blue)? 10
4. Total candies in the jar? 12
5. Simplified probability? 5/6
10.
A die is rolled. What is the probability of getting a prime number?
1. a)
2. b)
3. c)
4. d)
Answer:
Primes on a die: = 3 outcomes. (Note: 1 is NOT prime). .
11.
A survey shows that 15 out of 60 students prefer pizza, 25 prefer burgers, and the rest prefer tacos. What is the probability a random student prefers tacos?
Answer: 1/3
1. How many students prefer pizza? 15
2. How many prefer burgers? 25
3. Calculate: Total - Pizza - Burgers = Tacos 20
4. Write probability as fraction: Tacos/Total 20/60
5. Simplify the fraction 1/3
12.
A letter is chosen randomly from the word PROBABILITY. What is the probability of choosing a vowel? (Answer as simplified fraction)
Answer: 4/11
PROBABILITY has 11 letters. Vowels: O, A, I, I = 4 vowels. .
13.
A bag contains numbered balls 1-20. What is the probability of drawing a number that is BOTH even AND greater than 10?
1. a)
2. b)
3. c)
4. d)
Answer:
Even AND >10: = 5 outcomes. .
14.
In a standard deck, what is the probability of drawing a face card (Jack, Queen, or King)?
Answer: 3/13
1. How many Jacks in a deck? 4
2. How many Queens? 4
3. How many Kings? 4
4. Total face cards? 12
5. Write simplified probability 3/13
15.
A factory produces 500 items. Quality control finds 15 are defective. If 5 items are selected randomly, what is the probability that the first one is defective? (Express as percentage)
Answer: 3
1. How many defective items? 15
2. How many total items? 500
3. Write the probability fraction 15/500
4. Simplify the fraction 3/100
5. Convert to percentage 3