Percentage and Decimal Review - Video Tutorials & Practice Problems

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Converting Percentages and Decimals

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So now let's do a quick review of percentages and decimals. So the first thing we want to be able to do is be able to switch between percentages and decimals. So take a percentage and turn it into a decimal or a decimal and turn it into a percentage right? In both cases the idea is we have to identify where the decimal point is. Um And a lot of That's easy if you have a number like you know 15.23. But what if you just had the number 16? Right in this situation? The decimal point is implied at the end here. Right? So that's the decimal point after the 16. So if you don't see one it's gonna be at the end. Um and when we're going from percentage to decimal we're gonna move the decimal .2 spaces to the left. When we go percentage to decimal and when we're going from decimal 2% we're going to also move to places two places here but we're gonna move to the right. Cool. Alright so let's go ahead and practice a little bit. Um I'm just gonna keep this in the same video for this practice. So what I want you to do is uh why don't you pause the video real quick and do these and then continue and we'll go through them together. Alright so I'm guessing you pause the video and you're back now. So let's do this 50% and we're gonna convert it to a decimal. So we start in this one, right. The decimal is implied after the 50. So we're gonna move it two places to the left and we're gonna get a decimal of interest in blue .50. Alright .50 or .5 you can drop that last zero and it's okay. Alright Let's do this next 1 1.25%. So now we're gonna move it two places to the left and now our new decimals here we have to add a zero in there and we're gonna get .01-5 for 1.25%. Alright let's try the same thing with 120%. So we've got our decimal point right there. Move to to the left and we're gonna get 1.2 is equal to 120%. Same thing for 5% Over here are decimals here so we're gonna move it one space two spaces, fill it with the zero. And we are going to get a 00.5 for that one. So compare that one with 50%. The first one that we did right? You want to be able to see the difference between 5% and 50% notice we've got that 500.5 there. How about this next 1 31.34. We're just gonna move the decimal two to the left and get 20.3134 12.5% to to the left .125. So compare that with the 1.25% right above it. And here we have .5%. So notice comparing this to 5% and 50%. So we're gonna move it 12 spaces add a zero in there and we're gonna get 00.5 is 0.5%. Alright and 100%. Last one here. Move it to And we're gonna get one is the answer. They're just 1.0 just one. Cool. Let's do the same thing here with the decimals to percentage on the bottom. Alright so positive video real quick. Try these out and then let's do them together. Alright so you're back now let's go ahead and solve these uh decimals to percentage. So the first one here 10.34 we're gonna move to to the right to become a percentage 12. We're gonna get 34% for this first one. How about 10.61? Same thing 12, you're gonna get 61%. Uh Let me move out of the way here, 610.612. And we are going to get 6% .4512 will move to and we'll get 45.12% right? How about .0004. We're gonna also same process move it over to And we are going to get a decimal of .04. You can also write 0.04. Right? Uh and that is a percent right 0.04%. The last one here, the number one. Remember if it doesn't give us the decimal, it's implied at the end, So we're gonna move it 12 at the zeroes and we'll get 100% for one. Cool, so that is converting percentages and decimals. Let's move on to the next video.

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Calculating Percentage Change

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Alright. So now let's review how to calculate percentage change. So this is the amount that something has changed in percent. So if we started at 10 and now we are at 15, what is the percentage change from 10 to 15? This is going to be the formula that we use. So it's gonna be the church changing X over the original value of X. X. Being whatever we're trying to find the percentage change of. Right? So another way to think of the change in X. It's the new value for X minus the original value for X. Right? And we're going to divide that by the original value. So let's try this first example here. Um We've got last year's sales revenue totaled 505 150,000 current year. Excuse me. Current year sales revenue increased to 800,000, calculate the percentage change in sales revenue. Alright, So we're gonna use this formula and we are going to do the percentage change equals so percent change Equals um the change in X. So how do we calculate the change in X? It tells us that the the current year sales increased to 800. So this is our new value here. This is our original last year's value. So let's calculate this percentage change. Our new value being 800,000. I'm gonna put 800 K. Here for 1000 minus 550,000. 550 K. Divided by our original value which was 550 K. Alright, so we get 800 minus 5 50 is going to be 2 50 K. Over 5 50 K. And let's see what we get there. Our answer is going to be .4545. Alright, but is this answer in a decimal or percentage? It gives it to us as a decimal? Let's convert it to a percentage. So what we're going to take is our decimal and move it two places to the right, so move it two places to the right and it's gonna end up there. 45.45%. Cool. Alright, so in the next video, you guys are gonna practice this next one here.

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Problem

Problem

The price of Clutch Pizza was originally $12. Clutch decides that everyone deserves more pizza and lowers the price to $10. Calculate the percentage change in the price of Clutch Pizza.