percent problem

Question

In pre-algebra, I am given the following problem:

 

If 720 0f the 840 math students took beginning math first, what percent did not take beginning math first?

 

Can you help me

Answer 1

This problem tests some attention to detail.  Let's analyze it.

 

There are 840 total students.  That number becomes the base for our percent -- its is the what in percent of what?

 

Then 720 students took beginning math first, so how many did not take beginning math first?  840-720 = 120

 

120 is what percent (meaning per hundred) of 840?    120/840 = 0.142857

    and with 840 total, we would probably round that to 0.14 or 14%.    (The problem might specify.)

 

To check:  what is 14% of 840?  117.6    That's close.  It shows you the effect of rounding.

 

Oh, and what % of the students took beginning math first?   It is 100% - 14%, or 86%.

Let's see what 86% of 840 is:   0.86*840= 722   Again, close.

Make a note for word (story) problems, the word "of" usually means multiply.