Rounding Decimals
Rounding Decimals is a Grade 5 math skill from Illustrative Mathematics Chapter 5 (Place Value Patterns and Decimal Operations) where students round a decimal to a given place value by examining the digit immediately to its right: if 5 or greater, round up; if 4 or less, keep the same. All digits to the right of the target place are then dropped. This skill is essential for estimation, measurement, and everyday use of decimals.
Key Concepts
Property To round a decimal to a given place value, look at the digit to its immediate right. If the digit is 5 or greater, round up the digit in the target place. If the digit is 4 or less, keep the digit in the target place the same. All digits to the right of the rounded digit are dropped.
Examples Rounding 1.58 doubloons to the nearest tenth: The digit in the tenths place is 5. The digit to its right is 8. Since $8 \geq 5$, we round the tenths digit up to 6. So, 1.58 rounds to 1.6. Rounding 23.741 doubloons to the nearest hundredth: The digit in the hundredths place is 4. The digit to its right is 1. Since $1 < 5$, we keep the hundredths digit the same. So, 23.741 rounds to 23.74.
Explanation Rounding is a way to estimate a number by making it simpler while keeping its value close to what it was. The process involves deciding whether to increase a digit or keep it the same based on the value of the digit to its right. This is useful for dealing with money, measurements, or any situation where exact values are not necessary.
Common Questions
How do you round a decimal in Grade 5?
Identify the target place value. Look at the digit immediately to its right. If it's 5 or greater, increase the target digit by 1. If it's 4 or less, keep the target digit unchanged. Drop all digits after the target place.
What is the rounding rule for decimals?
Look at the digit one place to the right of where you want to round. 5 or more → round up. 4 or less → round down (keep the same). For example, rounding 1.58 to the nearest tenth: the hundredths digit is 8 ≥ 5, so round up to 1.6.
What chapter covers rounding decimals in Illustrative Mathematics Grade 5?
Rounding decimals is covered in Chapter 5 of Illustrative Mathematics Grade 5, titled Place Value Patterns and Decimal Operations.
What is an example of rounding a decimal to the nearest hundredth?
Round 23.741 to the nearest hundredth: the thousandths digit is 1, which is less than 5, so keep the hundredths digit at 4. The answer is 23.74.
Why is rounding useful for decimals?
Rounding simplifies decimal numbers for practical use — money, measurements, and everyday quantities. It allows for quick mental math and estimation while keeping numbers close to their actual values.