• 2 months ago
Transcript
00:00In this video, we are going to teach you a really cool trick.
00:05No, it has nothing to do with yo-yos, although you can learn a lot of tricks with a yo-yo.
00:11So what is this number trick?
00:14It's something cool called rounding numbers.
00:17Rounding numbers.
00:21Let's say Frankie loves playing tennis.
00:24He loves playing tennis so much, he has a huge collection of tennis balls.
00:29In fact, Frankie owns 39 tennis balls.
00:34His friends know he collects tennis balls,
00:37so one of his friends asks him,
00:39About how many tennis balls do you have?
00:43His friend isn't asking for the exact amount.
00:47His friend is asking,
00:48About how many tennis balls do you have?
00:52His friend could have also asked this way,
00:55Roughly how many tennis balls do you have?
00:59Frankie knows that 39 is just one less than 40,
01:04as you can see from this number line.
01:06So he answers,
01:07I have about 40 tennis balls.
01:09That's rounding.
01:12Rounding makes a number more simple
01:15when knowing the exact number isn't important.
01:19That's pretty awesome.
01:20Rounding makes a number more simple
01:22when knowing the exact number isn't important.
01:26In our example, Frankie rounded the number 39 up to the number 40.
01:32His friend didn't want to know the exact number of tennis balls.
01:36His friend asked for an estimate.
01:39Frankie has about 40 tennis balls.
01:44Rounding is especially common with bigger numbers.
01:47For example, did you know about 6 million people
01:51visit the famous Colosseum in Rome each year?
01:55Do exactly 6 million people visit the Colosseum each year?
01:59No.
02:00That's why we said about 6 million.
02:03The exact number was rounded so that the number we shared
02:07would be simple and easy to remember.
02:11That's what rounding does.
02:13Rounding makes a number more simple
02:15when knowing the exact number isn't important.
02:20It's used when we say words like about or roughly.
02:24We might say, there are about this many
02:27or there are roughly this many.
02:32Okay, now that we know what rounding is and what it does,
02:36we need to learn how to round numbers.
02:40Let's pick a random number, 46.
02:43Before we do any rounding, we need to review our place values.
02:48Do you remember place values?
02:50It's important to know our place values
02:52so we can know exactly how to round the number.
02:56What digit is in the ones spot?
03:00Yes, the number 6.
03:02This first spot is always the ones spot.
03:06What digit is in the tens spot?
03:11Uh-huh, the number 4.
03:13The second spot is always the tens spot.
03:17Great job!
03:19Now that we know the place values,
03:21let's round 46 to the nearest 10.
03:25You will always have two options,
03:27to round up or to round down.
03:30In this example, we will either round up to 50
03:34or we'll round down to 40.
03:37But which one do we need to do?
03:40To find out, we need to look at the digit
03:42before the spot we are rounding to.
03:45The digit before the 4 is 6.
03:48If you are rounding to the nearest 10,
03:50you always look at the ones spot.
03:54Okay, here is where we do the trick.
03:56If the spot before is 5 or more, round up.
04:00Let's say that again.
04:01If the spot before is 5 or more, round up.
04:06Alright, so the digit in the ones spot is the number 6.
04:11Are we going to round up or down?
04:14Yes, up.
04:16So this number will go up to 50.
04:19That is the nearest 10.
04:21We did it, we rounded a number.
04:2346 gets rounded up to 50.
04:27You did an awesome job.
04:29Let's do another one.
04:31Okay, how about the number 23?
04:34What digit is in the ones spot?
04:37Yes, the number 3.
04:39This first spot is always the ones spot.
04:42What digit is in the tens spot?
04:45Yes, the number 2.
04:47The second spot is always the tens spot.
04:51Now that we know the place values,
04:53let's round 23 to the nearest 10.
04:57Remember, you will always have two options,
04:59to round up or to round down.
05:02In this example, we will either round up to 30
05:05or we'll round down to 20.
05:09Next, we need to look at the digit before the spot we are rounding to.
05:14The digit before the 2 is 3.
05:17If you are rounding to the nearest 10,
05:19you always look at the ones spot.
05:22Okay, here is where we do the trick.
05:25If the spot before is 5 or more, round up.
05:28That's fun to say, let's say it one more time.
05:30If the spot before is 5 or more, round up.
05:34Alright, so the digit in the ones spot is the number 3.
05:38Are we going to round up or down?
05:42Yes, down.
05:44So this number will go down to 20.
05:47That is the nearest 10.
05:49That's how you round numbers.
05:5123 gets rounded down to 20.
05:55Great job!
05:57Let's use the trick on an even bigger number
06:00because it always works, no matter how big the number is.
06:05Okay, how about the number 544?
06:09What digit is in the tens spot?
06:13Yes, the number 4.
06:15Remember, the second spot is always the tens spot.
06:19What digit is in the hundreds spot?
06:23Yes, the number 5.
06:25The third spot is always the hundreds spot.
06:29Now that we know the place values, let's round 544 to the nearest hundred.
06:35You will always have two options, to round up or to round down.
06:40In this example, we will either round up to 600 or we'll round down to 500.
06:47But which one do we need to do?
06:50Well, we need to look at the digit before the spot we are rounding to.
06:55The digit before the 5 is 4.
06:58If you are rounding to the nearest hundred, you always look at the tens spot.
07:04Are you ready for the trick?
07:06You know it now.
07:07If the spot before is 5 or more, round up.
07:10That's fun to say. Let's say it again together.
07:13If the spot before is 5 or more, round up.
07:16Cool.
07:18Okay, so the digit in the tens spot is the number 4.
07:22Are we going to round up or down?
07:26Yes, down.
07:28So this number will go down to 500.
07:32That is the nearest hundred.
07:34And that's how you round numbers.
07:37544 gets rounded down to 500.
07:44Now you know the trick to round any number.
07:47If the spot before is 5 or more, round up.
07:50One more time.
07:51If the spot before is 5 or more, round up.
07:54Great job. You did awesome.