How to Estimate With Percents Using Friendly Numbers

0:00 How to estimate with percents, tips, sales, road trips, quick math, real life, it's everywhere. You need to know how to estimate with percents. Exact is great, you know, but closer. You just get it. You're just going to get it done faster. If you know how to estimate, you can use it in the real world. You want to round to a friendly number first, then use a percent you can do in your head, the friendly ones. 10% is divided by 10. It's one/10enth. It's one part out of 10 equal parts. 50%. That's half. So, you're just cutting that number in half. It's five out of 10 equal parts. 25% is a quarter. One out

0:45 of four equal slices, for example. Everything else will build from those. But as long as you know those 10%, 50%, 25%, we'll be able to figure it out. All right, example one, a sneaker sale. $68 sneakers are 10% off. So think to yourself, okay, the $68, that's really close to what? You can round 68 to 70. When you round 68 to 70, now finding 10% of 70 is pretty easy. 10% of 70 equals 7 because 100% equals 70. So one part out of 10 of 70 is 7. So the 10% of 68 is

1:33 approximately 7. It's not exactly seven. Remember we're rounding. We're finding approximates. So you'll save about $7 or just under $7. Example two. The quiz. 41 questions, 30% are word problems. So 30% of 41 if you're trying to figure out how many of them are word problems. So first just round 41 to 40. Round it to a friendly number. And then 10% of 40 equals 4. You're just moving the decimal over one spot like this. When you're finding 10%, you're just moving the decimal over one spot to right there.

2:19 Or you can think about it as one/10enth of 40. 30% is 310. 100% = 40. So 30% is 10% 10% 10%. So 4 + 4 + 4. And that gets us 12. 30% of 41 is approximately 12. Is it exactly 12? No. But again, that's not what we're doing here. It's about 12 word problems. Example three, the road trip. 162 miles total. You're 49% there. Here's your home. Here's You're going to 162 miles. You're about halfway, aren't you? Cuz 49% is 49 per 100.

3:07 and 49% of 162. That's tricky to do. We can just estimate that 49% is about 50% of the way. So 100 in 162 is about 160. Again, this isn't about getting the exact answer. This is about finding a quick close estimate so that you can use that information to help you. So, we're going to estimate 49% to 50%, cuz it's a friendly number and 162 to 160. Again, just to make it easier. Now, you're finding 50% of 160, which is half of 160. Half of 16 is 8. So, a half of 160 must be 80. So, it's about 80.

3:53 49% of 162 is approximately 80. This little symbol right here means approximately. Example four, the pizza vote. 83 kids voted. 24% picked pizza. Hm. What is 24% of 83? Again, neither one of those are very friendly numbers. 24% is about 25%. Remember, 25% means 25 per 100. 25 over 100 or 1/4. 83 is about 80. So 25% is one slice out of four. So you'd break it up. You'd have 20, 20,

4:38 20, and 20. That's 20 40 60 80. 25% of 80 equals 20. So 24% of 83 is approximately 20. About 20 kids. Another reason why understanding how to estimate and approximate is so important in math is because when you're not doing it, it's a great method to check your work. If you're able to understand your answer should be around this, it's a great indicator if you've gone wrong somewhere early on. Example five, the 15% tip. Dinner is $38.60. You're leaving a 15% tip.

5:24 Burger $14.50. Fries $510. Two shakes $19. Those must be some good shakes. Total $38.60. Tip 15%. What are you going to do? 15% of $38.60. Well, $38.60 is about 40. 10% of 40 equals 4. But you didn't want to leave 10%, you wanted to leave 15%. Well, 5% is half of 10%. So 5% has to be half of the 10% of 40, which was $4. So 5% of 40 must be $2. Then we

6:10 just put it all together. $4 plus $2 equals $6. Again, that's not exactly 15%, it's actually a little bit more than 15%. But the 10% plus the 5% equals the 15%. Here's the mistake that students often make. 30% of 40 equals 4. No, 10% of 40 equals 4. Remember, when you're finding 10% of a number, you're finding 10 parts out of 100 parts or one part out of 10 parts. They they mean the same thing. So 30% of 40 is not four. That's 10%. So moving the decimal only gives 10%.

6:58 So 100% equals 40. That means 10% must be four. This is one part out of 10 of these parts. So 30% would be three of those parts. Four, four, and four. All right, three challenges. Mild to spicy. You're going to pick the one that fits you, and you can do the other ones if you want, but you're going to start off with mild, medium, and then spicy. If you jump right to spicy, go for it. But if you get stuck, go back. Go back to medium. Then if you get stuck there, go back to mild. It's totally okay. All right. Mild, 10% of 92. You want to think about friendly numbers. Okay. Think about those.

7:46 Medium, 26% of 39. Again, make friendly numbers. Spicy 35% off of $59. About what would you pay? And here's another practice problem. about 21% of 149. All right. So once again, let's take a look at those three problems. We had mild 10% of 92. 10% of 92 would be you could keep to 10% cuz that's a friendly number. And we'll change 92 to 90. So 10% of 90. Now remember, whenever we're finding 10% of a number, you're

8:32 just you're just breaking it up into 10 parts or just move the decimal over one spot. So 10% of 90 is 9. So 10% of 92 is approximately 9. Nice job. 26% of 39. 26% of 39. That's not super friendly numbers. So, let's go with let's go with 25% because I know 25% is just breaking it up into a fourth of 40. And so that's like finding 1/4 of 40, which would be 10. So 26% of 39 is approximately

9:18 10. All right, let's keep going. Spicy 35% off for $59. About how much would you pay? This is a tricky one. All right, so let's let's change the 59 to 60 cuz that's a friendly number. And let's do um 10%. 10% 10% and then we'll do 5%. Because 10 10 and 5 get us 35%. So 10% of 60 is 6 and then another six

10:03 then another six. And then remember 5% must be half of whatever 10% was. So 5% must be three. So when we add this all up, we get 6 12 $18. We get $21 off. So $21 off and it's 35% off of 59. So it's not saying how much would you save, it's saying how much would you pay? So, in keeping with um our approximates here, cuz it's about how much you would pay, we would do we could do just simply 60 minus 20.

10:50 So, it's going to be about $40. Could I have done minus 21? Yeah, you could have. I could It'd be about 39. But again, trying to keep it with super friendly numbers. Okay, back to your practice problem. Make sure you put this in the comments. About 21% of 149. 21% of 149. Think about friendly numbers. This one I'm not going to do here on the video, but I will leave the answer pinned in the comments. So, make sure you check it out. And uh if you got something different, explain to me what you did, what was your process. I will see you in the next video. Thank you so much for taking the time to watch this. Don't forget to like, subscribe, all the things. All right, we'll see you

11:36 in the next video. Take care. Bye.