What Does It Mean to Estimate Decimals?
Estimation is like making a smart guess!
When we estimate sums and differences of decimals, we round the numbers to make them easier to work with in our heads. This helps us quickly check if our exact calculations make sense.
How to Estimate with Decimals
1️⃣ Round each decimal to the nearest whole number (or tenth if needed)
2️⃣ Add or subtract the rounded numbers in your head
3️⃣ Compare your estimate to the exact answer to check reasonableness
Let's Practice with Examples!
Example 1: Shopping Spree!
Emma wants to buy a toy for $12.79 and a book for $8.45. About how much money should she bring?
Estimate $12.79 + $8.45:
Round $12.79 → $
Round $8.45 → $
Great job! $12.79 rounds to $13 and $8.45 rounds to $8. So $13 + $8 = $21.
The exact total is $21.24, so your estimate was close!
Example 2: Baking Cookies
Liam needs 3.75 cups of flour but only has 1.9 cups. About how much more does he need?
Estimate 3.75 - 1.9:
Round 3.75 →
Round 1.9 →
Awesome! 3.75 rounds to 4 and 1.9 rounds to 2. So 4 - 2 = 2 cups needed.
The exact difference is 1.85 cups, so your estimate was very close!
Parent Tips 🌟
- Make it real: Use grocery receipts to practice estimating totals before checking the exact amount.
- Estimation games: Play "guess the total" with prices from ads or restaurant menus.
- Number line help: Draw number lines to visualize where decimals fall between whole numbers.