Mary is chosen to inspect pencil sharpeners to make sure they work for each 10 she inspects she finds 2 that are bad 4arebad pencil sharpeners how many are good

Question

Mary is chosen to inspect pencil sharpeners to make sure they work for each 10 she inspects she finds 2 that are bad if Mary finds four bad pencil sharpeners how many are good?

Answer 1

Hi Aina,

 

This question involves proportions.  Mathematically, the way to handle proportions is:

   - Set it up as fractions equal to each other.
   - Be very careful where you put the x (the unknown)
   - Cross-multiply to solve.

So our formula is:

 2        4
__  =  __
10       X

When we cross-multiply we get:

2X = 40  So, X=20

Now, the question is not how many sharpeners did she inspect (which is 20), but how many sharpeners are good.  So, this involves simple subtraction which I know you can handle.

 

BTW- In my mind I added periods and capital letters to make sense of the question as you wrote it.  Hopefully, I figured that out correctly.  Let me know if you need further help.

Paul L.