Working with Percentages Examples

What's 80% of 40?

Our first proportion is the percentage. 80% means 80 out of 100.

We need to find 80% of 40, so 40 is a denominator.

Now we solve for x. Multiply both sides by (100)(40) to obliterate those denominators.

Divide by the coefficient of x.

So 80% of 40 is 32. Noice.

30% of what number is 15?

First things first, y'all. Our first proportion is the percentage. 30% means 30 out of 100.

We need to find 30% of some number x, so x is a denominator this time.

Then we multiply both sides by 100x. So long, denominators.

Awesomesauce. Finish up by dividing both sides by 30.

Nailed it. 30% of 50 is 15.

What percent of 60 is 20?

Our first proportion is the percentage. We don't know our % this time, so it's our unknown, x.

20 is some unknown part of 60, so that's a ratio of 20:60.

Everything's all set up, so we're ready to solve for x. Multiply both sides by (100)(60).

Solid. Now divide by 60 to get x by itself.

There we go: our missing percent is 33.333...%.

What's 90% of 5?

Let's use the equation method this time. First we convert 90% into a decimal by bopping the decimal point to the left two places.

90% = 0.9

Now translate the equation.

What (x) is (=) 90% of (multiply) 5?

x = 0.9 × 5

No shame in using a calculator.

x = 0.9 × 5 = 4.5

What's 9% of 300?

We're gonna go with the equation method again. First convert 9% to a decimal. The decimal point boogies two spots to the left.

9% = 0.09

Translation time. What's 9% of 300?

x = 0.09 × 300

All that's left is the actual multiplying.

x = 0.09 × 300 = 27