Rounding Decimals

For Elementary Students

What Does Rounding Mean?

Rounding means changing a number to a nearby number that's easier to work with.

Think about it like this: If your friend lives 3.7 miles away and someone asks "how far?" you might say "about 4 miles" — that's rounding!

The Rounding Rule

Look at the digit to the right of where you're rounding.

• If it's 5 or more → round up
• If it's 4 or less → round down (keep the same)

Rounding to the Nearest Whole Number

Example: Round 7.3 to the nearest whole number.

Step 1: Which whole numbers is 7.3 between?

• It's between 7 and 8

Step 2: Look at the tenths place: 3

• Is 3 less than 5? Yes!

Step 3: Round down → 7

Example: Round 7.8 to the nearest whole number.

Step 1: Between 7 and 8

Step 2: Look at tenths: 8

• Is 8 ≥ 5? Yes!

Step 3: Round up → 8

Rounding on a Number Line

Visual way to see rounding:

7.3 is closer to 7
    ↓
7 ──.3─ 7.5 ──── 8

7.8 is closer to 8
              ↓
7 ──── 7.5 ──.8─ 8

7.5 is exactly in the middle, so we round up to 8.

Rounding Money

Money is a common place to round!

Example: Round $4.36 to the nearest dollar.

Look at the tenths (dimes): 3

• 3 < 5 → Round down

Answer: $4

Example: Round $4.89 to the nearest dollar.

Look at tenths: 8

• 8 ≥ 5 → Round up

Answer: $5

For Junior High Students

Rounding to the Nearest Tenth

The tenths place is the first digit after the decimal point.

Example: Round 3.47 to the nearest tenth.

Step 1: Identify the tenths place: 4

Step 2: Look at the digit to the right (hundredths): 7

Step 3: 7 ≥ 5 → Round up

• 3.4 becomes 3.5

Answer: 3.5

Example: Round 8.23 to the nearest tenth.

Tenths: 2 Look right: 3 3 < 5 → Keep the same

Answer: 8.2

Rounding to the Nearest Hundredth

The hundredths place is the second digit after the decimal point.

Example: Round 5.678 to the nearest hundredth.

Step 1: Identify hundredths place: 7

Step 2: Look right (thousandths): 8

Step 3: 8 ≥ 5 → Round up

• 5.67 becomes 5.68

Answer: 5.68

Example: Round 2.341 to the nearest hundredth.

Hundredths: 4 Look right: 1 1 < 5 → Keep same

Answer: 2.34

Rounding to Different Places

The Special Case: Exactly .5

When the digit is exactly 5 with nothing after it, round up.

Example: Round 7.5 to nearest whole number.

Tenths = 5 → Round up → 8

Example: Round 3.25 to nearest tenth.

Hundredths = 5 → Round up → 3.3

Rounding Multiple Times

Be careful! Round only once, not multiple times in a row.

Wrong way:

• Start: 4.748
• Round to hundredth: 4.75
• Then round to tenth: 4.8 ✗

Right way:

• Start: 4.748
• Round directly to tenth: Look at 4 (hundredths), 4 < 5 → 4.7 ✓

Checking Your Work

Question: Does my answer make sense?

• 8.7 rounded to nearest whole should be close to 8 or 9 (not 12!)
• 5.23 rounded to nearest tenth should be between 5.2 and 5.3

Real-World Uses

Money: Prices rounded to nearest cent ($3.456 → $3.46)

Measurements:

• "The board is 7.8 feet long, so about 8 feet."
• "I ran 5.3 miles, approximately 5 miles."

Science: Recording data to appropriate precision

Sports: Times and distances (race time: 10.27 seconds → 10.3 seconds)

Estimating with Rounding

Example: About how much is 7.8 + 4.3?

Round first:

• 7.8 → 8
• 4.3 → 4
• Estimate: 8 + 4 = 12

Actual: 7.8 + 4.3 = 12.1 (our estimate was close!)

When to Round

Before calculating: For quick estimates

After calculating: For final answer when exact precision isn't needed

Reporting: When sharing results (test score: 87.6% → "about 88%")

Practice