Rounding Numbers

Digits below 5 round down, while digits above 4 round up. Here are some examples. Be careful when the digit to the left of the last digit rounded is 9. The digit in bold determines whether to go up or down.

1. Round to the nearest whole number: 45.31 to 45 – 45.5 to 46 – 59.88 to 60
2. Round to the nearest ten: 45.31 to 50 – 44.89 to 40 – 599.88 to 600
3. Round to the nearest hundred: 489 to 500 – 449 to 400 – 5998 to 6000

Rounding Decimal Numbers

The same applies about going up or down and the digit 9. The digit in bold determines whether to go up or down. Here are some examples.

1. Round to the nearest tenth: 6.349 to 6.3 – 6.382 to 6.4 – 5.99 to 6.0
2. Round to the nearest hundredth: 6.349 to 6.35 – 6.382 to 6.38 – 5.9966 to 6.00
3. Round to the nearest thousandth: .4019 to .402 – .75312 to .753 – .899915 to .900

Scientific Notation

This is used with very large whole numbers and very small decimal numbers. The first number is at least 1, but less than 10. It may have one or more digits to the right of the decimal. This is followed by an x sign. This is followed by a power of 10. Here are some examples.

1. 93,000,000 = 9.3 x 10⁷ (There are 7 digits to the right of the decimal.)
2. 258,600,000,000 = 2.586 x 10¹¹ (There are 11 digits to the right of the decimal.)
3. 0004 = 4 x 10^-4 (There are 4 digits to the left of the decimal. Note the minus sign.)
4. .000000056 = 5.6 x 10^-8 (There are 8 digits to the left of the decimal. Note the minus sign.)