The following colored pens were placed in a backpack.
• 3 red
. 3 black
• 2 blue
. ? purple
How many purple pens need to be in the backpack in
order for the probability of pulling out a red pen, no
replacing it, then pulling out a purple pen to be 1/15?

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

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step-by-step explanation:

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