Percents — Basic example

- [Instructor] A pair of jeans that regularly costs $40 is on sale for 30% off. As part of a promotion, each customer will also receive an additional discount on the marked sale price at the cash register. If the final price of the jeans was $22.40, what additional discount was applied to the marked sale price? All right, this is interesting and useful, 'cause we need to know what we're gonna pay for our jeans. All right, so the regular price is $40, we're gonna assume everything is in dollars. It's on sale for 30% off. Well if you're 30% off that means it's going to cost 70% of the regular price. So let's put 70% of 40, so let's multiply that times 0.7, which is the same thing as 70%. 40 times 0.7, that's going to be equal to $28, yeah seven times four is 28, .7 times 40 is also going to be 28. All right so it's gonna be $28 would just be the 30% off, but the final price of the jeans was 22.40. What additional discount was applied to the marked sale price? Well to figure that out we can just divide. We can say well what fraction of 28 is 22.40? 22.40 divided by, divided by 28. Well this is going to be equal to, let's see, 28 and actually you could even rule out, I'll do the arithmetic right over here, so 28 goes into 22.40, so I'll get the decimal right over here, 28 doesn't go into 22, but it does go into 224. Let's think about it, how many times does 28 go into 224? I don't know, maybe seven times, let's see if this works. So it goes seven times, seven times eight is 56, seven times two is 14 plus five is 19. And then if we were to subtract, let's see we could make this a 14 regrouped from here, this would be a one, but then we remove from here, this would be an 11, 14 minus six is, 14 minus six is eight, 11 minus nine is two. Okay so we actually could have gotten one more in there, so let's see, this is going to go, 28 goes into 224 exactly eight times, eight times, eight times eight is 64, 64, eight times two is 16 plus six is 22, no remainder. So this is 80% of the marked down price. So if this is 80%, if this is 80% of this, then the additional discount that was taken is going to be 20% because once you take 30% off you'd expect to pay $28, but you only paid 80% of that, so they took off another 20%, they took off another 20%. If you take off 20%, then you're going to pay 80% of the price.