Pippa has a box containing n pens.
there are only black pens and red pens in the box.
the number of black pens in the box is 3 more than the number of red pens.
pippa is going to take at random 2 pens from the box.
the probability that she will take a black pen followed by a red pen is
9
35
find the possible values of n.
show clear algebraic working.

Respuesta :

The possible values of N from the given probability parameters is; N equals 15 or 21

How to Solve Algebra Problems?

We are told that;

Number of pens in the box = N

Let the number of red pens be x

Thus; number of black pens = x + 3

Thus;

x + x + 3 = N

x = (N - 3)/2

The probability that she will take a black pen followed by a red pen is;

P(she will take a black pen followed by a red pen) = (x + 3)/N * x/(N - 1)

Plugging in he relevant values and solving for N gives ;

Solving for N gives N equals 15 or 21

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