Rounding Numbers 

Rounding off numbers is an easy way to remember specially big numbers involving 6 or 7 digits or even more. It is also an easier way to remember decimal numbers. Rounding off numbers can be done to nearest tens, hundreds or thousands as needed.

Practical application or necessities of rounding off:

• When we are buying vegetables of the market suppose we bought 7 kgs 253 gm. We usually refer to as 7kgs 250 gm. That is 253 gm is rounded off to 250 gm. That is to the nearest tens.
• When Alice was asked by her friend what is her age she told 12 years. The exact age of Alice is 12 years 1 months 5 days. She has rounded off her age.
• Grey bought a mobile phone for $252.85. When he was asked by his friends what is the price of the mobile Grey said $250. This is rounding off.

This rounding off numbers finds a wide application in our day to day life.

There are certain rules that are followed while rounding off numbers

Rule I: When a number ends with 5, 6, 7, 8, 9 then we round it off to the next nearest tens.

For example:

48 will be rounded off to 50

15 will be rounded off to 10

Rule II: When a number ends with 1, 2, 3, 4 then we round it off to the previous nearest tens.

For example:

42 will be rounded off to 40

24 will be rounded off to 20

Now this rounding off is case specific. That is we have to confirm what are we rounding off to?

Rule III: If we are rounding to nearest 10 tens then 5 is the mid position. Number ending with 5 or more should be rounded off to next nearest tens

For example:

35 will be rounded off to 40

Rule IV: If we are rounding off to nearest hundreds then also we need to find the mid position.

For example:

Round off 437 to nearest hundreds

In this case we need to find the two hundreds between which 437 lies. We know that 437 lies between 400 and 500. The mid position between 400 and 500 is 450. So we need to check whether the number given (here 437) is more than 450 or less than 450. If the given number is 450 or more then we would round the number to 500 and if it is less than 450 then we will round it off to 400. In this example 437 will be rounded off to 400

Rule V: If we are rounding off to nearest thousands we need to find the mid position

For example:

Round off 4750 to nearest thousands

The two thousands between which 4750 lies is 4000 and 5000. The mid position is 4500. We know that if a number is equal to or more than mid position then  slide it to next thousands, hundreds or tens (as required). Here we need to round off to nearest thousands hence it will be 5000 as 4750 is greater than mid value (4500)

5th Grade Math

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