Finding a percentage of a quantity

A stall sold four hundred chicken rice sets in one month. 40 percent of them were takeaway orders. How many of the sets were takeaway orders? Let's draw it. Here's one bar for all four hundred sets. That's everything the stall sold. The whole bar is one hundred percent. Percent means out of one hundred, and the whole is always one hundred percent. We want 40 percent of those sets. 40 percent means 40 out of one hundred. So shade 40 percent of the bar. Here it is, in blue. Now the working, and this is the part that always works. Write the percentage over one hundred, then times the whole. 40 over one hundred, times four hundred. Now cancel. Four hundred divided by one hundred is 4, so it becomes 40 times 4. That's one hundred and sixty. So 40 percent of four hundred sets is one hundred and sixty sets. And that's the rule. Whatever the percentage is, even something like 46 percent, you write it over one hundred and times the whole, the very same way.

Your turn. Here's the question. Out of the same four hundred sets, one hundred were sold on a Sunday. What percentage of the sets is that? Pause and work it out. Try it first. Pause if you like. Let's finish it together. Nothing has changed about the whole. It's still four hundred sets, and four hundred sets is still one hundred percent. The Sunday sets are the part. So write the part over the whole. That's one hundred over four hundred. Then, to turn a part into a percentage, times it by one hundred percent. One hundred over four hundred, times one hundred percent, is 25 percent. And that's the second rule. So here are the rules to keep. Percent means out of one hundred. And the whole is always one hundred percent. To find a percentage of a whole, write the percentage over one hundred and times the whole. And to turn a part into a percentage, write the part over the whole and times one hundred percent.