Atotal of 24 out of 40 sixth graders buy hot lunch each day. what percent of these students do not buy hot lunch each day?

60% of student don't buy a hot lunch. 
The simple way of doing it is by taking both numbers and dividing them.  24 divided by 40= 0.6  Since percents are part of a whole, we need to multiply by 100  0.6 times 100 equals 60.
Easy and accurate. 

24 out of 40 is 60%

So subtract 24 and 40
40 - 24 = 16

Now there is 16 out of 40 people that do not buy hot lunch

Now 16 out of 40 is 40%

So 40% of the students did not buy Hot Lunch, hope it helped
 

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.