Numbers - Rounding Whole Numbers

 


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Rounding Whole Numbers

What is rounding? Rounding means changing a given number to the nearest ten, hundred, thousand, and so on. When rounding a number, look at the place value of the number and what multiples it is between.

 

Rounding Rules:

Rule 1:If the number to the right of the place you are rounding is less than 5 round to the lower multiple.

Rule 2:If the number to the right of the place you are rounding is 5 or greater, round to the higher multiple.

Examples:
462 - 400 or 500 Answer: 500

432 - 400 or 500 Answer: 400

452 - 400 or 500 Answer: 500

 

 

How to Round Whole Numbers

Step 1: Choose the place value that you want to round a number to - meaning the 10's, 100's, 1 000's or another place value.

ie: Round 6 458 to the nearest hundred - In this case we are rounding to the hundred's place.

Step 2: Decide what two multiples the number you are rounding is between.

ie: We are rounding to the hundred's place so we would choose multiples of 100. So: 6 458 is between 6 400 and 6 500

Step 3: Look to the digit in the place immediately right of the place you are rounding to and use the rounding rules to decide whether you move it up to the higher multiple or round to the lower multiple.

ie: Look in the ten place of the number 6 458. We see a 5, so we must round to the higher number.

Therefore: Round 6 458 to the nearest hundred = 6 500

 

Why would you want to round a number?

Rounding is a form of estimation that you use when an approximation is good enough.

For example when you are buying a TV at the store. The cost might be marked at $279.00. You could say it is about $300.00.

Rounding is also good to use so that you know what to expect for an answer. It is good to use this skill when you are plugging numbers into a calculator.

Ex. Let's say you are adding up your expenses for the month. Power: $230, Telephone: $79.68 Rent: $470 Car Payment: $822. To get a good approximation of the money you will need you could round to the closest hundred:

Power: $230 would be$200
Phone $79.68 would be $100
Rent: $470 would be $500
Car: $822 would be $800

Total: $1601 which is close to the estimated total of $1600

 

 

Assignment: Rounding Whole Numbers (word document)