Hello and welcome to Tutoring Hour!
In this video, we’ll show you how to round off whole numbers to the nearest ten, to the nearest hundred, and to the nearest thousand using a simple trick.
Rounding is nothing but adjusting digits to make calculations easy and quick.
Let’s think of this scenario
Debby is buying electronic gadgets for two hundred, twelve dollars and seven hundred, eighty nine dollars.
Adding these two amounts is taking her time.
But what if the prices were two hundred dollars and eight hundred dollars?
She could tell the total is a thousand dollars in a split second, Right?
Rounding makes numbers simpler and easy to work with.
Let’s move on to the know-how of rounding using a number line,
and understand the underlying place value concept.
We'll try rounding off the number 26 to its nearest 10.
Let’s do that by looking at the digit in the tens place.
We have 2 in the tens place and 6 in the ones place.
We know 26 is more than 2 tens but less than 3 tens.
Therefore, 20 and 30 become our benchmarks.
Now, we need to decide if we will round down to 20 or round up to 30.
Let’s put that on our number line.
Starting off with 20 and going up to 30.
We can see that 26 is between 20 and 30, but it is much closer to 30.
Let’s animate our number line, and make it look like a little number hill.
And imagine a log dropped at 26.
Which side will it roll off?
Obviously, to 30!
Now that implies, we need to round up.
But what if the log was dropped at 22?
22 is closer to 20.
It is clear that the log will roll back to 20.
So, here we are rounding down.
That was fun!
But is there a way to round off without a number line?
Yes!
There’s a pretty simple rule to round off numbers.
Let’s try rounding the number one hundred, fifty four to the nearest ten.
First, we need to figure out the digit we are gonna round off the number to.
Which is the tens place, in this case.
We have the number 5 there.
With that done, we'll shift our focus to the digit that is on its right.
If you see a 0, 1, 2, 3, or 4,
then keep the targeted digit unchanged,
and drop the digit on the right of the targeted digit to zero,
That is rounding down.
One hundred, fifty-four rounds down to one hundred, fifty.
But you may ask, what if we see a 5, 6, 7, 8, 9, to the right of the targeted digit as in One hundred, fifty seven?
Then we need to add 1 to the targeted digit. So, we have 5 plus 1 making it 6,
And change the digit to the right of the targeted digit to zero,
This is rounding up.
The number one hundred, fifty-seven is rounded up to one hundred, sixty.
That’s a pretty cool rule!
Now, let’s move on to rounding the number eight hundred, ninety-five to the nearest hundred.
Our targeted digit in the hundreds place is 8.
So, are we gonna round up or round down?
Any guesses?
Let's look at the number to the right of our targeted digit.
The tens place. It has a 9.
So, it is pretty clear, we are gonna round up to nine hundred.
Let’s upskill and try rounding off four thousand, five hundred, seven to the nearest ten.
The digit we are gonna target here is 0.
The number to its right is 7.
So, four thousand, five hundred, seven rounds up to four thousand, five hundred, ten.
That was quick!
How about rounding the same number to the nearest hundred?
Our targeted digit is now the number 5, the digit in the hundreds place.
We have the number zero to its right, in the tens place.
It is pretty clear we will round down the number keeping the hundreds place as it is.
So, four thousand, five hundred, seven rounds down to four thousand, five hundred.
Pretty straightforward stuff this is!
Let’s move one more rung up the ladder, and try rounding the same number to the closest thousand.
The targeted digit in the thousands place is 4.
And the digit 5, to its right,
makes it apparent that we need to round up the number to five thousand.
Looks like your all set to round off and simplify numbers in your head and use this technique efficiently in and outside the classroom!
Now, it’s your turn. If you want to learn in spades and practice in plenty,
then tutoringhour.com is the place to be.
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