Rounding Numbers

Grade 3 · mathematics · 100 practice problems · read aloud

🔊 Listen to this explanation

Rounding Numbers: Making Numbers Simpler! 🎯

Rounding helps us make numbers simpler and easier to work with. We often round numbers to the nearest ten or hundred to estimate answers quickly.

How to Round to the Nearest Ten

  1. Find your place: Look at the number and find the ones place (the last digit).
  2. Look next door: Look at the digit in the ones place. This is your helper digit.
  3. Follow the rule:
    • If the helper digit is 0, 1, 2, 3, or 4, the tens digit stays the same.
    • If the helper digit is 5, 6, 7, 8, or 9, the tens digit goes up by 1.
  4. Finish it: All digits to the right become zeros.

Let's See Some Examples!

Example 1: Round 47 to the nearest ten.

🔹 The number is 47. The ones digit is 7.

🔹 7 is 5 or more, so the 4 (in the tens place) goes up to 5.

🔹 47 rounds to 50.

Example 2: Round 132 to the nearest ten.

🔹 The number is 132. The ones digit is 2.

🔹 2 is 4 or less, so the 3 (in the tens place) stays the same.

🔹 132 rounds to 130.

Watch Out! Common Mistakes

🚫 Changing the wrong digit: Only the digit in the place you are rounding to can change. The ones place always becomes a zero when rounding to the nearest ten.

🚫 Forgetting the rule for 5: The number 5 is the boss! It always makes the number go UP. 35 rounds to 40, not 30.

Tips & Tricks

💡 The Hill Method: Imagine the numbers 0-9 are on a hill. 0-4 are on the downhill side (roll back down). 5-9 are on the uphill side (climb up to the next ten)!

💡 Number Line Helper: Draw a number line. If the number is in the first half (closer to the lower ten), round down. If it's in the second half (closer to the higher ten), round up!

Time to Practice!

Try rounding these numbers to the nearest ten:

  • 28 → ?
  • 65 → ?
  • 93 → ?
  • 114 → ?

Ask a friend or family member to give you numbers to round. The more you practice, the easier it gets!

Practice problems

6 of the 100, worked through step by step — try them before opening the answer.

1 64 + 37 = ?

Hint: When adding two numbers, start with the ones place and remember to carry over if needed.

Show the answer

Answer: 101

  1. Write the numbers vertically in your mind for alignment by place value. 64 + 37
  2. Start by adding the digits in the ones column (rightmost column). Ones column: 4 + 7 = 11. 11 is a two-digit number, so we split it: 11 = 10 + 1. We write down the 1 in the ones place of the answer and carry over the 10 (which is 1 ten) to the tens column.
  3. Now add the tens column, including the carry-over. Tens column: 6 (from 64) + 3 (from 37) + 1 (carried over) = 10. So the tens column sum is 10 tens, which is 100.
  4. Combine the results from the tens and ones columns. From
  5. 10 tens = 100 From
  6. 1 one = 1 So total = 100 + 1 = 101. Final answer: 101

Let's add 64 and 37 step-by-step.

2 75 + 28 = ?

Hint: When adding two-digit numbers, start with the ones place and then move to the tens place. If the ones digits add up to 10 or more, remember to carry over to the tens column.

Show the answer

Answer: 103

  1. Write the numbers vertically in your mind (or on paper). 75 + 28
  2. Start by adding the digits in the ones column (rightmost column). 5 (from 75) + 8 (from 28) = 13.
  3. Since 13 is a two-digit number, we break it into 10 and 3. Write down the 3 in the ones place of the answer, and carry over the 10 (which is 1 ten) to the tens column.
  4. Now add the digits in the tens column, including the carry-over. 7 (from 75) + 2 (from 28) + 1 (carried over) = 10.
  5. The result for the tens column is 10, which means 10 tens = 100. So we write 10 in the tens and hundreds places: 10 tens means 1 hundred and 0 tens.
  6. Combine the hundreds, tens, and ones: From
  7. 100 From
  8. 3 Together: 100 + 3 = 103. Final Answer: 103

Let's add 75 and 28 step-by-step.

3 1000 - 450 = ?

Hint: Think about subtracting hundreds and tens separately when working with larger numbers.

Show the answer

Answer: 550

  1. Write the numbers vertically in your mind (aligning by place value): 1000 - 450
  2. Start subtracting from the rightmost digit (ones place). In the ones place: 0 - 0 = 0. Write 0 in the ones place of the answer.
  3. Move to the tens place. In the tens place: 0 - 5 cannot be done without borrowing. So we look to the hundreds place.
  4. In the hundreds place of 1000, we have 0. We cannot borrow from 0, so we must go to the thousands place.
  5. The thousands place has 1 (meaning 1000). We borrow 1 from the thousands place: 1 thousand = 10 hundreds. So thousands place becomes 0, and hundreds place becomes 10.
  6. Now from the 10 hundreds, we borrow 1 hundred for the tens place. 1 hundred = 10 tens. So hundreds place becomes 9 (because 10 - 1 = 9), and tens place becomes 10.
  7. Now subtract in the tens place: We have 10 (after borrowing) - 5 = 5. Write 5 in the tens place of the answer.
  8. Subtract in the hundreds place: We have 9 (after borrowing) - 4 = 5. Write 5 in the hundreds place of the answer.
  9. Subtract in the thousands place: We have 0 (after borrowing) - 0 = 0. So thousands digit is 0, which we don’t write in front.
  10. Combine the digits: hundreds digit 5, tens digit 5, ones digit 0. That gives 550. Final answer: 550

We are solving: 1000 - 450 = ?

4 1000 - 350 = ?

Hint: Think about subtracting hundreds first, then tens, and combining the results.

Show the answer

Answer: 650

  1. Write the problem vertically to make it easier. 1000 - 350 _______
  2. Start subtracting from the rightmost column (ones place). The top number in the ones place is 0, and the bottom number is 0. 0 - 0 = 0 Write 0 in the ones place of the answer.
  3. Move to the tens place. The top number is 0, and the bottom number is 5. We cannot do 0 - 5 because 0 is smaller than 5. So we need to borrow.
  4. Look to the hundreds place. The hundreds digit in 1000 is 0, so we cannot borrow from there directly. We must go to the thousands place.
  5. Borrow from the thousands place: - The thousands place digit is 1 (meaning 1000). - We take 1 thousand and change it into 10 hundreds. - So now the thousands place becomes 0, and the hundreds place becomes 10. But the hundreds digit was 0, now it's 10.
  6. Now, from these 10 hundreds, we can borrow 1 hundred for the tens place. - 10 hundreds become 9 hundreds (in the hundreds place). - The 1 hundred we borrow becomes 10 tens in the tens place. - The tens place was 0, now it becomes 10.
  7. Now subtract in the tens place: Tens place: 10 (after borrowing) - 5 = 5. Write 5 in the tens place of the answer.
  8. Move to the hundreds place: Hundreds place: 9 (after lending to tens) - 3 = 6. Write 6 in the hundreds place of the answer.
  9. Move to the thousands place: Thousands place: 0 (after lending to hundreds) - 0 = 0. Since this is the leading digit, we don't write it. So the result is 650. Final check: 1000 - 350 = 650.

Let's solve 1000 - 350 step by step.

5 1000 - 250 = ?

Hint: Think about subtracting hundreds first, then tens. You can break the larger number into parts to make it easier.

Show the answer

Answer: 750

  1. Write the problem. 1000 - 250
  2. Start subtracting from the rightmost digit (units place). The units digits are 0 and 0. 0 - 0 = 0 So, the units digit of
  3. Move to the tens place. The tens digits are 0 and 5. We cannot do 0 - 5 directly because 0 is smaller than 5. So we need to borrow from the hundreds place.
  4. Look at the hundreds place. The hundreds digit of 1000 is 0, so we cannot borrow directly from there either. We must go to the thousands place.
  5. Borrow from the thousands place. The thousands place digit is 1. We change the thousands place: 1 becomes 0. The hundreds place becomes 10 (after borrowing 1 thousand = 10 hundreds).
  6. Now borrow from the hundreds place to the tens place. The hundreds place currently has 10, but we need to give 1 hundred to the tens place. Reduce hundreds place from 10 to 9. 1 hundred = 10 tens, so add 10 to the tens place (which was 0), making it 10.
  7. Now subtract the tens place. Tens place: 10 (after borrowing) - 5 = 5.
  8. Subtract the hundreds place. Hundreds place: 9 (after lending to tens) - 2 = 7.
  9. Subtract the thousands place. Thousands place: 0 (after initial borrowing) - 0 = 0.
  10. Write the result. Hundreds digit = 7, tens digit = 5, units digit = 0.

Let's solve 1000 - 250 step by step. the answer is 0. So the answer is 750. Final check: 750 + 250 = 1000, which confirms the subtraction is correct. ANSWER: 750

6 1000 - 375 = ?

Hint: Consider subtracting hundreds first, then tens, then ones

Show the answer

Answer: 625

  1. Start with 1000
  2. Subtract 300: 1000 - 300 = 700
  3. Subtract 70: 700 - 70 = 630
  4. Subtract 5: 630 - 5 = 625

The answer is 625.

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