Question

Probability with and without replacement:

An activity book has 21 pages of crossword puzzles, 18 pages of cryptograms, and 12 pages of mazes. Bianca randomly selects a page, completes the activity, and then randomly selects another page to complete.

What is the probability that Bianca first completes a maze and then completes a crossword puzzle.

Ans:

42/425

28/289

21/88

33/51

Answer 1

28/289

Explanation:

First we need to find the total number of pages.

21 = crosswords puzzles

18 = cryptograms

12 = mazes

So there are:

21 + 18 + 12 = 51 pages total

The probability that Bianca will complete a maze first is 12/51.

The probability that her next choice will be a crossword puzzle is 21/51

Now to find the probability that Bianca will do a maze followed by a crossword puzzle is:

12/51 x 21/51

We can simplify the values by dividing everything by 3

Maze then crossword puzzle = 4/17 x 7/17

Maze then crossword puzzle = 28/289