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Welcome to the article There are 15 identical pens in your drawer nine of which have never been used On Monday you randomly choose 3 pens to take with. On this page, you will learn the essential and logical steps to better understand the topic being discussed. We hope the information provided helps you gain valuable insights and is easy to follow. Let’s begin the discussion!

There are 15 identical pens in your drawer, nine of which have never been used. On Monday, you randomly choose 3 pens to take with you, use each one of them to write, and put them back in the drawer in the evening. On Tuesday, you randomly choose once again 3 pens to take with you. Find the probability that none of the 3 pens you took with you on Tuesday has ever been used.

Answer :

Answer: p = 0.9337

Step-by-step explanation: from the question, we have that

total number of pen (n)= 15

number of pen that has never been used=9

number of pen that has been used = 15 - 9 =6

number of pen choosing on monday = 3

total number of pen choosing on tuesday=3

note that the total number of pen is constant (15) since he returned the pen back .

probability of picking a pen that has never been used on tuesday = 9/15 = 3/5

probability of not picking a pen that has never been used on tuesday = 1-3/5=2/5

probability of picking a pen that has been used on tuesday = 6/15 = 2/5

probability of not picking a pen that has not been used on tuesday= 1- 2/5= 3/5

on tuesday, 3 balls were chosen at random and we need to calculate the probability that none of them has never been used .

we know that

probability of ball that none of the 3 pen has never being used on tuesday = 1 - probability that 3 of the pens has been used on tuesday.

to calculate the probability that 3 of the pen has been used on tuesday, we use the binomial probability distribution

p(x=r) = [tex]nCr * p^{r} * q^{n-r}[/tex]

n= total number of pens=15

r = number of pen chosen on tuesday = 3

p = probability of picking a pen that has never been used on tuesday = 9/15 = 3/5

q = probability of not picking a pen that has never been used on tuesday = 1-3/5=2/5

by slotting in the parameters, we have that

p(x=3) = [tex]15C3 * (\frac{2}{5})^{3} * (\frac{3}{5})^{12}[/tex]

p(x=3) = 455 * [tex]0.4^{3} * 0.6^{12}[/tex]

p(x=3) = 455 * 0.064 * 0.002176

p(x=3) = 0.0633

thus probability that 3 of the pens has been used on tuesday. = 0.0633

probability of ball that none of the 3 pen has never being used on tuesday = 1 - 0.0633 = 0.9337

Thank you for reading the article There are 15 identical pens in your drawer nine of which have never been used On Monday you randomly choose 3 pens to take with. We hope the information provided is useful and helps you understand this topic better. Feel free to explore more helpful content on our website!

Rewritten by : Brahmana