Round Off Rules for Numbers ~ BZU SCIENCE

Estimating is playing a vital role in mathematics. It has also become a handy tool in our everyday life. In everyday life, we have to estimate the length of time and lots of other physical quantities. Rounding off is one of the most important kinds of estimating. To round off a number means that we will have to make a number simpler. This simpler number should be very close to the actual number. No doubt, the result of rounding off is less accurate. Anyhow, it is easy for us to use the results of the rounding off numbers. For example, if we have a digit 83, it's rounding off value should be 80. Here, we will try to learn round off rules for decimals and whole numbers.

Round off Rules for Decimals

We have to round off decimals, not in mathematics but also other fields of life. If you want to round off decimals, you will have to follow some rules. The basic rules to round off decimals are given below;

1. First of all, you will have to decide the place value that you want to round off. We call this place value as the rounding digit. After deciding the rounding digit, you should look at the right digit of this rounding digit.

2. If the digit at the right side of the rounding digit is less than 5, you should not change the rounding digit. Anyhow, you will have to drop all the digits that are present to the right of the rounding digit.

3. If the digit at the right side of the rounding digit is greater than 5, you will have to add ‘1’ in the rounding digit. Just like the previous step, you will have to drop all the digits that are present to the right of the rounding digit.

4. In some cases, the rounding digit can also be equal to 5. If the rounding digit is equal to 5, you will have to add one in the rounding digit. You should also drop all the digits that are present to the right of the rounding digit.

Explanation of Round Off Rules for Decimals with Examples

After understanding the rules to round off decimals, you can easily round off the decimals. Here, we will try to explain this concept by solving examples. Round off the following decimals;

A. 4.7871

B. 3.1239

C. 7.1251

We will try to round off these decimals nearest to tenth place after the decimal point. First of all, we will try to solve the first example.

4.7871

In this example 4.7871, 8 is the rounding digit. On the ride side of the rounding digit of this example 4.7871, the digit is 7. As this digit is greater than 5, therefore, we will have to add one in the rounding digit. After removing the other digit, the example 4.7871 will become 4.79.

3.1239

2 is the rounding digit in this example 3.1239. 3 is the next digit on the right side of the rounding digit of this example 3.1239. As it is less than 5, therefore, we don’t need to add one in the rounding digit. After rounding off, its answer will become 3.12.

7.1251

Here, 2 is the rounding digit in this example 7.1251. On the right side of the rounding digit of this example 7.1251, the next digit is 5. That’s why we will have to add one in the rounding digit. The answer to this example will be 7.13.

BODMAS Rule

Difference between Rational and Irrational Numbers

Round off Rules for Whole Numbers

In some cases, we have to round off the whole numbers. To round off the whole numbers, we will have to follow some rules. Here, we will follow the following rules to round off whole numbers.

1. To round off the whole numbers, first of all, we will have to find the place value of the digit that we want to round off. This digit is also known as rounding digit. After finding the rounding digit, we will have to look at the digits that are at the right side of the rounding digit.

2. If the digit right to the rounding digit is less than 5, we should not add anything in the rounding digit. Anyhow, we will have to change all the digits right to rounding digit. We will have to change these digits with zeros.

3. If the digit right to the rounding digit is greater than 5, we will have to add one in the rounding digit. After adding one in the rounding digit, we will have to change all the digits with the zeros.

4. Now, if the digit right to the rounding digit is equal to 5, we should also add one in the rounding digit. Just like the other two steps, we should also change the remaining digit right to the rounding digit with zeros.

Examples of Rounding Off Whole Numbers

After understanding the rules for rounding off whole numbers, we can easily solve the questions relevant to the whole numbers. Round off the following whole numbers;

A. 4253

B. 3248

C. 4387

To solve these examples, first of all, we should try to find the rounding digit. We are going to round off these whole numbers in the tenth place.

4253

In this example 4253, 2 is the rounding digit. The digit to the right of the rounding digit in this example 4253 is 5. According to the rounding off rules, we will have to add one in rounding digit and we will have to replace all the other digits with zeros. After rounding off, this number will become 4300.

3248

In the example 3248, 2 is the rounding digit. After the rounding digit, the next digit is 4. As it is less than 5, therefore, we should not add one in the rounding digit. After rounding off, its solution will be 3200.

4387

3 is the rounding digit in the example 4387. Now, we will have to look at the digit at the right side of the rounding digit. In the example of 4387, 8 is the next digit. As it is greater than five, therefore, we will have to add one in the rounding digit. The solution to this example will be 4400.

Everyday Uses of Rounding Off Numbers

While learning mathematical concepts, most of the people don’t know their uses in everyday life. If you are learning rules to round off numbers, you should know that there are various uses of the rounding off numbers in the everyday life. Here, we will explain some uses of the rounding off numbers in everyday life.

1. After learning these rules, you can handle the mismatch between the fractions and decimals. For example, after dividing a fraction, if we get the answer 0.666666..., we will have to round off this answer. Its reason is that we will have to work with only two or three digits only.

2. You can also apply these rules to change the multiplied results. For example, if we multiply 0.25 with 0.75, the answer will be 0.1875. If you want to work with just two points after the decimal point, its answer will be 0.19.

3. It is also the best way to find out the value of the sales tax. While buying various things from the shop, it will be difficult for us to pay tax in decimals. When we will apply the round off rules, we can easily get the exact value.

4. You can also use these rules to do calculations in your mind. To do calculations in your mind, you will have to find the nearest value of different things.

5. If we want to remember 8,213,409, it will be difficult for us. After applying the round off rules, we can easily remember it. After rounding off, we can read it as 8 million.