Praxis Core Academic Skills for Educators: Mathematics (5733)Statistics and ProbabilityMedium
A scientist is studying the growth of a certain bacteria. She observes that the population doubles every hour. If she starts with 100 bacteria, what is the probability that a randomly selected bacterium at the 3-hour mark was one of the original 100 bacteria?
- A1/8
- B1/16
- C1/2
- D1/4
Show answer & explanationAnswer & explanation
Correct answer: A. 1/8
After 1 hour, the population is 100 * 2 = 200. After 2 hours, 200 * 2 = 400. After 3 hours, 400 * 2 = 800. The original 100 bacteria are still present among the 800, so the probability is 100/800 = 1/8.
Why the other options are wrong
- B. This would be the probability after 4 hours.
- C. This would be the probability after 1 hour.
- D. This would be the probability after 2 hours.
Basic Probability
Probability is a measure of the likelihood that an event will occur, expressed as a number between 0 and 1.
- Calculated as (Number of favorable outcomes) / (Total number of possible outcomes).
- A probability of 0 means the event is impossible, 1 means it's certain.
- Applies to situations with random outcomes.
Memory trick: Favorable outcomes over Total possibilities.