Part, portion and percentage

So, do you think you can calculate percentages? Then it's time for more difficult percentage problems. There are four percentage problems in this video and the easiest one comes first. Feel free to pause when you see this symbol and to try to solve it for yourself first. Let's go.

The weight of the contents of a can of Kuchiliketa Cola is 320 grams. If the can contains 35 grams of sugar, what percentage is it? We have the part and the whole, and we want to know the share in percent. Take the part divided by the whole. The part is 35, the whole is 320, 35 divided by 320.

Calculate and round to 0,11. A can of Kuchiliketa Cola contains 11% of sugar. Here, we know the part and the whole and calculated the percentage. Let's take another one. Here's a bag of chips.

It weighs 250 grams and 36% of that weight is fat. How many grams of fat does the bag contain? We now have the whole and the share in percent, and we want to know what the part is. Take the whole and multiply it by the share- 250 grams times 36 hundredths equals 99 grams. Now one more example.

You buy a large soda at Pierre Olson’s hamburger place. The cup contains 90 gm of ice. You know that the ice makes up 37. 5% of the cups contents. What is the combined weight of the soda and ice?

This time we know the part and the share in percent, and we want to know what the whole is. Take the part divided by the share and you get the whole. The part is 90, divided by the share which is 0,375. That's 240. The cup's contents weigh 240 grams.

Is it hard to remember which formula to use in each case? Look at this triangle. The letters stand for part, whole, and share in percent. Put your finger over the value you want and read the formula. If, for example, you want to know the whole, cover W, you have P divided by S, left, so you take the part divided by the share.

In the same way, you cover P if you want the formula for the part and you cover S if you want the formula for the share. Make up a memory rule for the letters P, W, S in that order so you can always recreate the triangle when you need to use it. There's one more thing that could be a bit tricky and to follow this, it might be helpful for you to do the lesson on a change factor. Look at this. A pair of jeans costs 675 kroner after 25% off.

How much did it cost before the sale? To calculate this, you take the new price divided by the change factor. That's 675 divided by 0,75, which is 900. The original price of the jeans was 900. You can think of it this way.

The old price is X. X times the change factor is 675. To get X alone on one side, divide both sides by the change factor. You get the old value equals the new value divided by the change factor. If you remember the formula, you don't have to solve the equation every time.

Here it is, the old value equals the new value divided by the change factor. These are four ways to solve problems with percent. Together with the change factor they contain everything you need to solve most percentage problems you will ever encounter.