Estimate sums, differences and products of decimals

key notes :

Understanding Estimation

• Estimation helps in quickly finding approximate answers.
• It is useful for checking reasonableness of calculations.

Rounding Decimals

To estimate, round decimals to the nearest whole number or one decimal place.

• Example: 4.73 rounds to 5, and 2.89 rounds to 3.

Estimating Sums

Round each decimal and then add the numbers.

• Example: 6.48 + 3.27 → Round to 6 + 3 = 9 (Estimated sum).

Estimating Differences

Round each decimal and subtract the numbers.

• Example: 9.85 – 4.32 → Round to 10 – 4 = 6 (Estimated difference).

Estimating Products

Round decimals before multiplying for easier calculations.

• Example: 7.92 × 4.08 → Round to 8 × 4 = 32 (Estimated product).

Using Compatible Numbers

Choose numbers that are easy to compute mentally.

• Example: Instead of 4.97 + 3.06, use 5 + 3 = 8.

Checking Reasonableness

Compare estimated results with exact answers to see if they are close.

• If the estimated and exact answers are far apart, check for errors.

Application in Real Life

• Used in shopping (estimating total cost), cooking (approximating ingredient amounts), and budgeting.

Learn with an example