Estimate differences: word problems

Key notes :

🔑 Key Points to Remember
  • Estimate means to find an approximate answer, not the exact one.
  • To estimate, we usually round numbers to the nearest tens, hundreds, or thousands before subtracting.
  • Estimation helps us check reasonableness of answers and solve quickly.
  • Use words like about, nearly, close to, or approximately in estimated answers.
✨ Steps to Estimate Differences
  • Read the word problem carefully.
  • Identify the numbers to be subtracted.
  • Round the numbers (to nearest 10, 100, or 1000 as needed).
  • Subtract the rounded numbers.
  • Write the estimated answer.
📝 Examples

Example 1:
A school has 742 students. About 389 students went on a trip. Estimate how many students stayed back.

  • Step 1: Round 742 → 700 (nearest hundred)
  • Step 2: Round 389 → 400 (nearest hundred)
  • Step 3: Subtract: 700 – 400 = 300
    ✅ Estimated Answer: About 300 students stayed back.

Example 2:
A farmer harvested 1,246 apples on Monday and sold 873 apples. Estimate how many apples are left.

  • Step 1: Round 1,246 → 1,200
  • Step 2: Round 873 → 900
  • Step 3: Subtract: 1,200 – 900 = 300
    ✅ Estimated Answer: About 300 apples are left.

Example 3:
A shop had 3,178 pencils. It sold 2,643 pencils. Estimate how many pencils remain.

  • Step 1: Round 3,178 → 3,200
  • Step 2: Round 2,643 → 2,600
  • Step 3: Subtract: 3,200 – 2,600 = 600
    ✅ Estimated Answer: About 600 pencils remain.
💡 Tips
  • If the question asks for a quick guess, always estimate instead of solving exactly.
  • Use estimation to check if your exact subtraction is reasonable.
  • Sometimes rounding to nearest tens gives better accuracy, other times to nearest hundreds is enough.
🎯 Practice Word Problems
  • A factory produced 4,892 toys in January and sold 3,467 toys. Estimate how many toys are left.
  • There were 2,135 books in the library. About 1,879 books were borrowed. Estimate how many books are still in the library.
  • A bus can carry 965 people in a week, but only 478 people traveled last week. Estimate how many seats were empty.
📌 Conclusion:


Estimation is a quick way to solve subtraction problems in real life. It gives an answer that is close to the actual difference and helps us save time.

Learn with an example

🎯 Kelsey just started working at a French restaurant. Last week, she polished a combined total of 981 small and large glasses. If Kelsey polished 292 small glasses, about how many large glasses did she polish? Choose the better estimate.

Subtract the number of small glasses polished from the total number of glasses.

981 − 292 = ?

Round each number to the nearest hundred.

981 – 292 = ?
1,000 – 300 = 700

700 is the better estimate.

🎯 Last year a total of 864 passengers landed at Somerville’s airport. However, only 589 had on-time arrivals. About how many passengers did not have on-time arrivals at Somerville’s airport last year? Choose the better estimate.

Subtract the number of passengers who had on-time arrivals from the total number of passengers.

864 − 589 = ?

Round each number to the nearest hundred.

864 – 589 = ?
900 – 600 = 300

300 is the better estimate.

🎯 A crayon company recently changed its labels. It currently has 991 crayons in stock, 886 of which have the new label. How many crayons with the old label does the company have in stock? Choose the better estimate.

Subtract the number of crayons with the new label from the total number of crayons.

991 − 886 = ?

Round each number to the nearest hundred.

991 – 886 = ?
1,000 – 900 = 100

100 is the better estimate.

Let’s practice!