Estimate sums

Key notes :

🎈1. Understanding Estimation

  • Estimation: The process of finding an approximate value rather than an exact answer.
  • Purpose: Helps in quickly assessing the magnitude of numbers and making reasonable guesses without performing exact calculations.

🎆2. Strategies for Estimating Sums

  1. Rounding Numbers:
    • Round to the Nearest Ten: Round each number to the nearest ten and then add.
    • Example:
      • Numbers: 43 and 28
      • Rounded Numbers: 40 (43) and 30 (28)
      • Estimated Sum: 40 + 30 = 70
  2. Rounding to the Nearest Hundred:
    • Round to the Nearest Hundred: Round each number to the nearest hundred and then add.
    • Example:
      • Numbers: 145 and 238
      • Rounded Numbers: 100 (145) and 200 (238)
      • Estimated Sum: 100 + 200 = 300
  3. Using Compatible Numbers:
    • Find Easy-to-Add Numbers: Choose numbers that are easy to add mentally.
    • Example:
      • Numbers: 56 and 29
      • Compatible Numbers: 60 (56) and 30 (29)
      • Estimated Sum: 60 + 30 = 90
  4. Estimating with Front-End Rounding:
    • Add the Leading Digits: Focus on the most significant digits to estimate.
    • Example:
      • Numbers: 167 and 389
      • Front-End Digits: 100 (167) and 400 (389)
      • Estimated Sum: 100 + 400 = 500

🎇3. Practice Problems

  1. Problem 1:
    • Estimate the sum of 82 and 47.
    • Solution:
      • Round to the nearest ten: 80 (82) and 50 (47)
      • Estimated Sum: 80 + 50 = 130
  2. Problem 2:
    • Estimate the sum of 254 and 168.
    • Solution:
      • Round to the nearest hundred: 300 (254) and 200 (168)
      • Estimated Sum: 300 + 200 = 500
  3. Problem 3:
    • Estimate the sum of 74 and 29.
    • Solution:
      • Use compatible numbers: 70 (74) and 30 (29)
      • Estimated Sum: 70 + 30 = 100

🧨4. Tips for Effective Estimation

  • Choose the Best Rounding Strategy: Depending on the numbers, rounding to the nearest ten, hundred, or using compatible numbers may be most effective.
  • Check for Reasonableness: After estimating, ensure that the estimated sum makes sense in relation to the numbers being added.
  • Practice Regularly: Regular practice with different numbers helps improve estimation skills.

Learn with an example

▶️ Estimate the sum by rounding each number to the nearest thousand and then adding.

7,787 + 1,001

The sum is approximately___________.

Round each number to the nearest thousand.

7,787 + 1,001 = ?

8,000 + 1,000 = ?

Now add:

8,000 + 1,000 = 9,000

The sum is about 9,000.

▶️ Estimate the sum by rounding each number to the nearest thousand and then adding.

9,383 + 5,687

The sum is approximately_________.

Round each number to the nearest thousand.

9,383 + 5,687 = ?

9,000 + 6,000 = ?

Now add:

9,000 + 6,000 = 15,000

The sum is about 15,000.

🔥Estimate the sum by rounding each number to the nearest hundred and then adding.

666 + 711

The sum is approximately ———.

Round each number to the nearest hundred.

Now add :

700 + 700 = 1,400

The sum is about 1,400.

Let’s practice!