Day 3: Basic Probability Puzzles #5

Objective

In this challenge, we practice calculating probability.

Task

There are 10 people about to sit down around a round table. Find the probability that 2 particular people will sit next to one another.

Answer : 2/9

Day 3: Basic Probability Puzzles #6

Objective

In this challenge, we practice calculating probability.

Task

Bag XX contains 5 white balls and 4 black balls. Bag YY contains 7 white balls and 6 black balls. You draw 1 ball from bag XX and, without observing its color, put it into bag YY. Now, if a ball is drawn from bag YY, find the probability that it is black.

Answer : 29/63

Day 3: Basic Probability Puzzles #7

Objective

In this challenge, we practice calculating probability.

Task

A firm produces steel pipes in three plants.

Plant AA produces 500 units per day and has a fraction defective output of 0.005. Plant BB produces 1000 units per day and has a fraction defective output of 0.008. Plant CC produces 2000 units per day and has a fraction defective output of 0.010. At random, a pipe is selected from the day’s total production and it is found to be defective. What is the probability that it came from plant AA?

Answer : 5/61

Day 3: Basic Probability Puzzles #8

Objective

In this challenge, we practice calculating probability.

Task

In a certain city, the probability of a resident not reading the morning newspaper is 12, and the probability of a resident not reading the evening newspaper is 25. The probability they will read both newspapers is 15.

Find the probability that a resident reads a newspaper (i.e.: the morning, evening, or both papers).

Answer : 9/10