The following colored pens were placed in a backpack.• 3 red. 3 black• 2 blue. ? purpleHow many purple pens need to be in the backpack inorder for the probability of pulling out a red pen, noreplacing it, then pulling out a purple pen to be 1/15?
Mathematics · High School · Tue Nov 03 2020
Answered on
The number of purple pen is 2
Explanation:
Number of red pens = 3
Number of black pens = 3
Number of blue pens = 2
Number of purple pens = ?
Probability =
Total number of pens = 3 + 3 + 2 + x
= 8 + x
The probability of pulling out a red pen =
Total number of pens become = 8 + x - 1
= 7 + x
Probability of pulling out a purple pen =
According to the question:
Solving the equation:
If x = 2 then,
Therefore, the number of purple pen is 2