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Rounding off to the nearest 5

Rounding off to the nearest 5 can sometimes be forgotten because teachers either don't know how to explain it or they don't see the need in doing it.

Today we are going to have a look at how to round off to the nearest 5. Rounding off to the nearest 5 can be quite confusing for learners if not taught properly.   

Start with a number line, draw a number line for the learners and number it from 0 to 10.  

Mark the 0 , 5 and 10

Tell your learners, for a number between 0 and 5, you always count backwards to 0, or forward to 5. For a number between 5 and 10, they always have to count backwards to 5 but forward to 10.

We start with 1 digit numbers:

1 , 3 , 7 and 9

For 1:

Draw a new number line and number it from 0 - 10.  

At first you can let learners use the number line to show how they jump from one number to another.

For 1, let them jump backwards from 1 to 0.

Then jump forward from 1 to 5. 

 Now, from 1 back to 0, they've only jumped once but from 1 to 5 they had to jump 4 times.  You can ask the learners now if they can see that jumping from 1 to 0 is closer than jumping from 1 to 5.

Learners obvious answer should be yes, and that they will also see that jumping to 0 is faster and closer.  So if 1 is rounded of to the nearest 5, the answer will be 0.

The next number to round off is 3.

The same here, let learners draw a number line, number it from 0-10 and do the same with 3.  Let the learners jump back from 3 to 0 and forward from 3 to 5.

They will tell you now, that from 3 to 0 they had to jump 3 times but from 3 to 5 they only jumped 2 times. 

3 rounded off to the nearest 5 is then equal to 5.

Getting the hang of this?    GOOD!!!

The next number is 7

Again... draw a number line, this time, the number lies between 5 and 10.

Let the learners now jump from 7 back to 5 and then from 7 to 10.

They will see that they jumped back 2 times but forward they've jumped 3 times.  They will be able to tell you that jumping to 5 is closer than jumping to 10.  

The last example for a 1 digit number is 9.

Use your number line, number from 1-10 and jump from 9 back to 5 and from 9 forward to 10.

They can see that you have to jump 4 times to get to 5 but only once to get to 10.  9 rounded of to the nearest 5 is then equal to 10.

It is very important to do a lot of these 1 digit exercises with the learners!!!

Starting with bigger numbers:

Tell your learners that, when working with bigger numbers and rounding off to the nearest 5 they ALWAYS have to look at the units. The last number!!

Lets start with 13.

They can still use the same number line, numbered from 1-10 as they are only going to use the units.

Rounding 13 off to the nearest 5, we only look at the 3 because that is the unit. 

On your number line, you can see that jumping from 3 to 5 is closer, which means that 13 rounded off to the nearest 5 will be equal to 15.  Remember that the 1 is at the place value of the tens, which still has to be included in your answer.

Even bigger numbers:

18977

Ok, bigger number, not a bigger problem.  Still remember that we only look at the units. (We don't forget about the other numbers) we just use the units to round off to the nearest 5.

18977 - rounded of to the nearest 5 =

The unit digit is 7

Ok, we use the same number line. WHY? Because, we only look at units when rounding off to the nearest 5.

On the number line, again you will see that 7 is between the numbers 5 and 10.  Jumping to 5 is closer than jumping to 10.  Only the unit digit changes, which then becomes 5.

18977 rounded off to the nearest 5 then, is equal to 18975.  Can you see that the rest of the numbers did not change but only the last digit?

What happens now if I get a BIGGER number??

Nothing changes, you use the same number line, numbered from 0-10, jump forward or backwards and see which one is closer.

Lets take the number 1986788

The unit digit is 8.  Closer to 10?? Right, but what happens now?  

8 is closer to 10, which means that the 8 becomes 10, but in the units place we can only write one digit.

That means the 8 becomes 10, but we only write the 0 and carry the 1 over to the next place value.  The tens.  The tens place value gets 1 more. You add it to the number already there.

Lets see:  1986788 rounded off to the nearest 5 is equal to : 1986790

Can you see that now, the units changed as well as the tens but the rest of the numbers were still not affected?

Rounding off to the nearest 5 can be the most difficult to round off to

Learners are not used to rounding off to 5, but rather to 10, 100 or a 1000.

It took me a while to get all my learners to round off to 5, but I am glad that I started with rounding off to 5.

It seems easier now to get learners to round off to 10, 100 and 1000 because they know now at which digit or place value to look at.

Hope this lesson will also work for someone else. 

*Please note that all images were done by myself and inserted here.

Enjoy your day!!!