1. Rounding
Rounding simplifies numbers by expressing them to the nearest unit, ten, hundred, or decimal place.
Key Rules:
- Round up if the digit is 5 or higher.
- Round down if the digit is less than 5.
Examples:
- Nearest 10: 156 160
- Three Decimal Places: 0.4563948 0.456
Why Round?:
- Makes calculations easier.
- Useful for estimating totals in shopping or planning.
2. Estimation
Estimation gives a rough answer, often used to check the reasonableness of detailed calculations.
Steps:
- Round numbers to simpler values (nearest 10, 100, etc.).
- Perform the calculation.
- Adjust up if necessary to ensure you have enough of what’s needed.
Examples:
- Buying carpet for rooms:
- Room 1: (3.2 \, {m} * 2.7 \, {m} \approx 3 \, {m} * 3 \, {m} = 9 \, {m}^2)
- Room 2: (1.16 \, {m} * 2.5 \, {m} \approx 1 \, {m} * 2.5 \, {m} = 2.5 \, {m}^2)
- Total: (9 + 2.5 = 11.5 \, {m}^2) Round up to 12 ( {m}^2).
3. Practical Uses
- Shopping: Quickly estimate totals by rounding prices (e.g., \$24.99 \$25).
- Time: Estimated Time of Arrival (ETA) uses speed and distance for rough arrival times.
4. Special Cases
Tradesperson Estimates:
- Estimates include time, material costs, and a contingency (~10–20%).
- Estimates are not binding, but quotes are legally binding if no extra work is added.
5. Benefits of Estimation Skills
- Cross-check detailed calculations for accuracy.
- Quickly evaluate budgets, bills, or projects.
- Confidence in everyday problem-solving without relying solely on a calculator.
Estimation is a practical skill that ensures you’re prepared, whether shopping, planning a project, or checking calculations.