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📏 Detailed Explanation of Estimate Differences

Estimating differences means finding a number that is close to the real answer when we subtract one number from another. It helps us check if an answer is sensible without working out the exact subtraction. This is very useful in Year 3 Maths and perfect for Key Stage 2 learners.

❓ What is Estimating Differences?

When we estimate differences, we are making a good guess about how much one number is less than another. Instead of subtracting exactly, we round the numbers to make the calculation easier and quicker.

🔢 How to Estimate Differences by Rounding

  1. Look at the numbers you need to subtract. For example, 46 − 29.
  2. Round each number to the nearest ten.
    • 46 rounds to 50
    • 29 rounds to 30
  3. Subtract the rounded numbers.
    50 − 30 = 20
  4. This is your estimated difference. It’s close to the exact answer but much quicker to work out.

🔄 Why do We Round Numbers?

Rounding makes numbers easier to work with. When you round to the nearest ten, you change numbers to the closest multiple of ten. For example:

  • 43 rounds to 40 because 43 is closer to 40 than 50.
  • 87 rounds to 90 because 87 is closer to 90 than 80.

🎯 Simple Example of Estimating Differences

Let’s say you want to estimate the difference between 73 and 38:

  • Round 73 to 70 (nearest ten).
  • Round 38 to 40 (nearest ten).
  • Now subtract: 70 − 40 = 30.

The estimated difference is 30. The exact difference is 35, so 30 is a quick and sensible estimate.

💡 Tips for Practising Estimating Differences

  • Always try to round the numbers before subtracting.
  • Remember to round each number separately.
  • Use estimating differences to check if your real subtraction answer looks right.
  • Practice with different numbers, especially ones in your daily life, like prices or distances.

Estimating differences is a fun and useful skill to help you solve subtraction problems quickly and check your work in Year 3 Maths!

📝 20 Examination-Style Questions on Estimate Differences for Year 3

✅ Multiple Choice Questions

  1. Estimate the difference: 48 − 23 ≈
    • a) 20
    • b) 25
    • c) 30
    • d) 35
  2. What is the estimated difference of 76 minus 41?
    • a) 30
    • b) 40
    • c) 50
    • d) 60
  3. Estimate 134 − 88 by rounding to the nearest 10.
    • a) 40
    • b) 50
    • c) 60
    • d) 70
  4. Which is the best estimate for 59 − 27?
    • a) 20
    • b) 25
    • c) 30
    • d) 35
  5. Estimate 102 − 49 by rounding both numbers to the nearest 10.
    • a) 50
    • b) 60
    • c) 70
    • d) 80

✏️ Fill in the Blanks

  1. Estimate the difference: 92 − 45 ≈ ______ (round both numbers to the nearest 10).
  2. Round 67 and 29 to the nearest 10. Then estimate 67 − 29 = ______.
  3. If you round 150 and 74 to the nearest 10, the estimated difference is ______.
  4. Estimate 88 − 53 by rounding to the nearest 10. The answer is ______.
  5. Round 123 and 79 to the nearest 10. The estimated difference is ______.

✍️ Short Answer Questions

  1. Explain how to estimate the difference between 85 and 38 by rounding.
  2. Estimate the difference: 147 − 92. Show your working.
  3. Round 56 and 38 to the nearest 10. What is the estimated difference?
  4. Estimate the difference between 70 and 28 by rounding.
  5. How would you estimate 234 − 189?

📖 Word Problems

  1. Sarah had 96 apples and gave 48 to her friend. Estimate how many apples she has left using rounding.
  2. A bus has 128 passengers. 79 get off. Estimate how many passengers are left on the bus.
  3. Tom read 172 pages and his sister read 95 pages. Estimate how many more pages Tom read.
  4. There are 205 pencils in the box, and 143 were used. Estimate how many pencils are left.
  5. Emma scored 87 in her test and her brother scored 44. Estimate by rounding the difference between their scores.

📚 Answers to Examination-Style Questions on Estimate Differences

  1. Estimate the difference between 74 and 29.
    Round 74 to 70 and 29 to 30.
    70 − 30 = 40.
    The estimated difference is 40.
  2. Estimate the difference between 56 and 18.
    Round 56 to 60 and 18 to 20.
    60 − 20 = 40.
    The estimated difference is 40.
  3. Estimate the difference between 93 and 67.
    Round 93 to 90 and 67 to 70.
    90 − 70 = 20.
    The estimated difference is 20.
  4. Estimate the difference between 105 and 58.
    Round 105 to 110 and 58 to 60.
    110 − 60 = 50.
    The estimated difference is 50.
  5. Estimate the difference between 48 and 22.
    Round 48 to 50 and 22 to 20.
    50 − 20 = 30.
    The estimated difference is 30.
  6. Estimate the difference between 81 and 44.
    Round 81 to 80 and 44 to 40.
    80 − 40 = 40.
    The estimated difference is 40.
  7. Estimate the difference between 67 and 39.
    Round 67 to 70 and 39 to 40.
    70 − 40 = 30.
    The estimated difference is 30.
  8. Estimate the difference between 122 and 58.
    Round 122 to 120 and 58 to 60.
    120 − 60 = 60.
    The estimated difference is 60.
  9. Estimate the difference between 39 and 15.
    Round 39 to 40 and 15 to 20.
    40 − 20 = 20.
    The estimated difference is 20.
  10. Estimate the difference between 75 and 49.
    Round 75 to 80 and 49 to 50.
    80 − 50 = 30.
    The estimated difference is 30.
  11. Estimate the difference between 90 and 27.
    Round 90 to 90 and 27 to 30.
    90 − 30 = 60.
    The estimated difference is 60.
  12. Estimate the difference between 68 and 33.
    Round 68 to 70 and 33 to 30.
    70 − 30 = 40.
    The estimated difference is 40.
  13. Estimate the difference between 54 and 29.
    Round 54 to 50 and 29 to 30.
    50 − 30 = 20.
    The estimated difference is 20.
  14. Estimate the difference between 99 and 50.
    Round 99 to 100 and 50 to 50.
    100 − 50 = 50.
    The estimated difference is 50.
  15. Estimate the difference between 134 and 76.
    Round 134 to 130 and 76 to 80.
    130 − 80 = 50.
    The estimated difference is 50.
  16. Estimate the difference between 41 and 19.
    Round 41 to 40 and 19 to 20.
    40 − 20 = 20.
    The estimated difference is 20.
  17. Estimate the difference between 88 and 62.
    Round 88 to 90 and 62 to 60.
    90 − 60 = 30.
    The estimated difference is 30.
  18. Estimate the difference between 77 and 51.
    Round 77 to 80 and 51 to 50.
    80 − 50 = 30.
    The estimated difference is 30.
  19. Estimate the difference between 95 and 44.
    Round 95 to 100 and 44 to 40.
    100 − 40 = 60.
    The estimated difference is 60.
  20. Estimate the difference between 62 and 25.
    Round 62 to 60 and 25 to 30.
    60 − 30 = 30.
    The estimated difference is 30.

🧠 Understanding the Steps to Estimate Differences

  • Step 1: Look at the numbers you need to subtract.
  • Step 2: Round each number to the nearest ten. For example, 74 becomes 70, 29 becomes 30.
  • Step 3: Subtract the rounded numbers to find the estimated difference.
  • Step 4: Write the answer as your estimate.

Remember, estimating differences helps you quickly find an answer that is close enough to the real one. It is useful when you want to check if your exact answer seems right. Keep practicing by rounding and subtracting to become confident at estimating differences.

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