Round Decimals

Grade 4 · decimals · 87 practice problems · read aloud

🔊 Listen to this explanation

Rounding Decimals

🧭 What is Rounding and Why is it Useful?

Rounding means making a number simpler but keeping its value close to what it was. We round decimals to make them easier to understand, compare, or work with. For example, if a pencil costs $1.97, you might say it costs "about $2.00" instead of counting exact change.

📝 How to Round Decimals: Step-by-Step

  1. Find your place: Look at the digit you are rounding to (like the tenths place).
  2. Look next door: Look at the digit immediately to the right.
  3. Four or less, let it rest: If that digit is 0, 1, 2, or 3, the rounding digit stays the same.
  4. Five or more, raise the score: If that digit is 5, 6, 7, 8, or 9, the rounding digit goes up by 1.
  5. Drop the tail: All digits to the right of the rounding place become zeros (or just disappear if they are after the decimal).

🔍 Visual Examples

Example 1: Round 3.47 to the nearest tenth.

  1. We are rounding to the tenths place. The digit is 4.
  2. Look next door to the hundredths place. The digit is 7.
  3. 7 is "five or more," so we "raise the score." The 4 becomes a 5.
  4. Drop the digits after the tenths place.
  5. Answer: 3.5

Example 2: Round 2.132 to the nearest hundredth.

  1. We are rounding to the hundredths place. The digit is 3.
  2. Look next door to the thousandths place. The digit is 2.
  3. 2 is "four or less," so we "let it rest." The 3 stays a 3.
  4. Drop the digits after the hundredths place.
  5. Answer: 2.13

⚠️ Common Mistakes to Avoid

  • Changing the wrong digit: Only the digit in the place you are rounding to can change. The others stay the same unless there's a "carry-over" from a 9 (like 3.96 rounds to 4.0, not 3.10).
  • Forgetting to drop digits: After rounding, you must drop all digits to the right of your rounding place. 5.78 rounded to the nearest tenth is 5.8, not 5.78.
  • Confusing the place values: Remember: Tenths (0.1), Hundredths (0.01), Thousandths (0.001).

💡 Tips & Tricks

  • Underline the place value you are rounding to. This helps you focus on the right digit.
  • Remember the rhyme: "Four or less, let it rest. Five or more, raise the score!"
  • Think of a number line. Is your number closer to the lower number or the higher number? For example, 7.28 is closer to 7.3 than to 7.2.

🎯 How to Practice

  • Use online math games that focus on rounding decimals.
  • Ask a friend or parent to give you numbers to round to different places.
  • Look for decimals in real life—on price tags, in recipes, on a ruler—and practice rounding them in your head!

Practice problems

6 of the 87, worked through step by step — try them before opening the answer.

1 3.47 × 2.5 = ?

Hint: Multiply the numbers as if they were whole numbers, then count the total decimal places in the factors to determine where to place the decimal point in the product.

Show the answer

Answer: 8.675

  1. Write the numbers without decimals to make it easier. 3.47 is the same as 347/100, and 2.5 is the same as 25/10. So 3.47 × 2.5 = (347 × 25) / (100 × 10) = (347 × 25) / 1000.
  2. Multiply 347 by 25. First, multiply 347 by 20: 347 × 20 = 6940. Next, multiply 347 by 5: 347 × 5 = 1735. Now add them: 6940 + 1735 = 8675.
  3. Now we have 8675 / 1000. Dividing by 1000 means moving the decimal point 3 places to the left. So 8675 becomes 8.675.
  4. Check decimal places in original numbers. 3.47 has 2 decimal places, 2.5 has 1 decimal place. Total decimal places: 2 + 1 = 3. So in the final answer, we need 3 decimal places. 8675 → 8.675 has 3 decimal places. Final answer: 8.675

Let's multiply 3.47 by 2.5 step by step.

2 3.47 + 2.86 = ?

Hint: When adding numbers with decimal points, make sure to align the decimal points vertically before adding each column from right to left.

Show the answer

Answer: 6.33

  1. Write the numbers one under the other, aligning the decimal points. 3.47 + 2.86 --------
  2. Start adding from the rightmost column (hundredths place). 7 hundredths + 6 hundredths = 13 hundredths. 13 hundredths = 1 tenth and 3 hundredths. Write down the 3 in the hundredths place, and carry over the 1 to the tenths place. 3.47 + 2.86 -------- .3 (with 1 carried to the tenths place)
  3. Add the tenths place, including the carry-over. 4 tenths + 8 tenths + 1 tenth (carried over) = 13 tenths. 13 tenths = 1 one and 3 tenths. Write down the 3 in the tenths place, and carry over the 1 to the ones place. 3.47 + 2.86 -------- .33 (with 1 carried to the ones place)
  4. Add the ones place, including the carry-over. 3 ones + 2 ones + 1 one (carried over) = 6 ones. Write down the 6 in the ones place. 3.47 + 2.86 -------- 6.33
  5. Combine all digits: 6 (ones), 3 (tenths), 3 (hundredths). So the final answer is 6.33. ANSWER: 6.33

Let's add 3.47 and 2.86 step by step.

3 Round 3.47 to the nearest tenth.

Hint: Look at the digit in the hundredths place to decide whether to round the tenths place up or keep it the same. For example, when rounding 2.83 to the nearest tenth, the 3 tells you to keep the 8.

Show the answer

Answer: 3.5

  1. Identify the digit in the tenths place. In 3.47, the digit in the tenths place is 4.
  2. Look at the digit to the right (the hundredths place). The hundredths digit is 7.
  3. Since the hundredths digit (7) is 5 or greater, we round the tenths digit (4) up by 1. 4 becomes 5.
  4. The digits after the tenths place become zero, so 3.47 rounded to the nearest tenth is 3.5.

4 Round 3.47 to the nearest tenth = ?

Hint: Look at the digit in the hundredths place to determine whether to round the tenths place up or keep it the same.

Show the answer

Answer: 3.5

  1. Identify the digit in the tenths place. In 3.47, the tenths digit is 4.
  2. Identify the digit in the hundredths place. In 3.47, the hundredths digit is 7.
  3. Since the hundredths digit (7) is 5 or greater, we round the tenths digit (4) up by 1.
  4. Rounding 4 up by 1 gives 5. The number becomes 3.5.

The answer is 3.5.

5 Round 7.89 to the nearest tenth = ?

Hint: Look at the digit in the hundredths place to determine whether to round the tenths place up or keep it the same.

Show the answer

Answer: 7.9

  1. Identify the digit in the tenths place. In 7.89, the digit in the tenths place is 8.
  2. Look at the digit to the right of the tenths place, which is the hundredths place. In 7.89, the hundredths digit is 9.
  3. Since the hundredths digit (9) is 5 or greater, we round the tenths digit up. Rounding 8 up gives 9.
  4. The number 7.89 rounded to the nearest tenth is 7.9.

6 Round 4.78 to the nearest tenth = ?

Hint: Look at the digit in the hundredths place to decide whether to round the tenths place up or keep it the same.

Show the answer

Answer: 4.8

  1. Identify the digit in the tenths place. In 4.78, the digit in the tenths place is 7.
  2. Look at the digit immediately to the right, which is the hundredths place. In 4.78, the hundredths digit is 8.
  3. Since the hundredths digit (8) is 5 or greater, we round the tenths digit (7) up by 1.
  4. Rounding 7 up by 1 gives 8. The digits to the right of the tenths place become zero, so 4.78 rounded to the nearest tenth is 4.80, which is written as 4.8.

The answer is 4.8.

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