Probability Questions

Multiple choice
  1. $\displaystyle \frac{3}{5}$
  2. $\displaystyle \frac{2}{5}$
  3. $\displaystyle \frac{1}{5}$
  4. $\displaystyle \frac{4}{5}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Prime numbers less than 50 are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47 (15 total). Primes less than 24 are: 2, 3, 5, 7, 11, 13, 17, 19, 23 (9 total). Probability = 9/15 = 3/5.

Multiple choice
  1. $\displaystyle \frac { 1 }{ 8 } $
  2. $\displaystyle \frac { 1 }{ 2 } $
  3. $\displaystyle \frac { 3 }{ 4 } $
  4. $\displaystyle \frac { 7 }{ 8 } $
  5. $\displaystyle \frac { 15 }{ 16 } $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The probability of at least one tail is 1 minus the probability of getting no tails (all heads). The probability of all heads in 3 tosses is (1/2)^3 = 1/8. Thus, 1 - 1/8 = 7/8.