Of the 20 students in a sixth grade math class, 30% of them went away for summer vacation. How many students went on summer vacation?

Step-by-step explanation:

First you need to set up a proportion like this

part/whole = % / 100 since a percent is always over 100%.

Then we see which number/percent goes where.

so since 30% is a percent we put it over the 100. Then we have 20 students which is the whole since we want to figure out how many students went on summer vacation. Now since we don’t know how many students went on vacation ofc we put a variable let’s say for example the variable X will represent the number of studnets that went in summer vacation.

Now our proportion should be like this:  X/20 = 30% / 100.

Now we would do cross multiplication. Like this 30 x 20 = 600. Since you can’t cross multiply X / 100 because we don’t have a number for the number is students that went in vacation as said before. Instead we do this we set up: X  times 100. Now we will do 600 divided by 100 and that will equal us 6. So X = 6 students that went on summer vacation. Hope this helps the image below will help you what I’m talking about. I tired my best I can to explain it.

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.