Rounding Numbers

Rounding Numbers

Why do we round numbers?

• Makes the numbers easier to work with

• Estimates value even if it is less precise

• Allows us to use irrational numbers like pi in calculations

Place Values

Each place value has a name. Everything after the decimal ends in "ths".

Multiple Choice

In 45.987, which number is in the tenths place?

• 4

• 5

• 9

• 8

Rounding Rules

• Decide which is the last digit to keep

• Leave it the same if the next digit is less than 5 (this is called rounding down)

• Increase it by 1 if the next digit is 5 or more (this is called rounding up)

Multiple Choice

Round 86 to the nearest 10.

• 80

• 85

• 90

Multiple Choice

Round 3.1416 to the nearest hundredths place.

• 3.142

• 3.14

• 3.1

• 3

Remember: Round AFTER calculations

• Order matters

• Don't round before calculating a problem