Rounding Off Numbers

Test
Materials

Rounding off is a kind of estimating. ‘Rounding’ means making a number simpler but keeping its value close to what it was. The result is less accurate, but easier to use.

Find the place value you want (the rounding digit) and look at the digit just to the right of it. If that digit is less than 5, do not change the rounding digit. If that digit is greater than or equal to 5, add one to the rounding digit and drop all digits to the right of it.

For Example:

  1. Round 368,971 to the nearest ten thousand? 368,971. Here, 6 is in the ten thousands place. As we know, 8 is larger than 4. Add 1 to the 6 and all the numbers to the right of the 7 become 0’s. 370,000.

  2. Round 35,327 to the nearest thousand? Since 3 is less than 4, we do not change the 5. Therefore, the answer is 35,000.

ROUNDING OFF DECIMALS

  1. If the first of the digits to be dropped is less than 5, then the last retained digit is unchanged. For Example: Round off 3.1416 to two decimal places. Since 4 is the last digit to be retained and the next digit to its right is less than 5.  Therefore, the answer is 3.14.

  2. If the first of the digits to be dropped is greater than 5, then the last retained digit is increased by 1. For Example: Round off 0.4536 to three decimal places. Since 6 is the digit to be dropped and it is greater than 5, the last retained digit is changed from 3 to 4. Therefore, the answer is 0.454.

  3. If the first digit to be dropped is 5 followed by zeros, then the last retained digit is kept unchanged if it is even. For Example: Round off 16.450 to one decimal place. The first digit to be dropped is 5 followed by a zero. The rounded number is 16.4.

  4. If the first digit to be dropped is 5 followed by a nonzero digit, then the last retained digit is increased by 1 . For Example: Round off 2.8530 to one decimal place. The first digit to be dropped is 5 followed by 3. The last digit to be kept is 8; it is increased to 9. Therefore, the answer is 2.9.