Bella keeps a supply of red, blue, and black pens in a drawer. The drawer has 13 red pens, 18 blue pens, and 8 black pens. If Bella wants a red pen, what is the minimum number of pens she has to pull out from the drawer to make sure she gets a red pen?
18 blue pens, 8 black pens and one red pen = ?
27
To make sure Bella gets a red pen, she needs to pull out at least one of each color pen plus one more red pen.
So, the minimum number of pens she has to pull out is:
1 red pen + 1 blue pen + 1 black pen + 1 more red pen = 4 pens.
Therefore, Bella needs to pull out at least 4 pens from the drawer to make sure she gets a red pen.
To find the minimum number of pens that Bella has to pull out to make sure she gets a red pen, we need to consider the worst-case scenario. In this case, the worst-case scenario is that Bella pulls out all the pens except for the red ones.
Given that there are 13 red pens, Bella needs to pull out all the pens except for the red ones, which are the blue and black pens. So, she needs to pull out all the 18 blue pens and 8 black pens before she gets a red pen.
Therefore, Bella needs to pull out a minimum of 18 + 8 = 26 pens in total to make sure she gets a red pen.