Understanding Decimal Sums and Differences
Decimals are everywhere!
Whether you're measuring ingredients for cookies or counting money, decimals help us be precise. Today we'll learn how to choose decimal numbers that add up to (or subtract to) a specific target number.
How to Find Decimals with Specific Sums/Differences
1️⃣ Understand place value - Know what each digit represents (tenths, hundredths)
2️⃣ Estimate first - Guess numbers that might work before calculating exactly
3️⃣ Check your work - Always add/subtract your numbers to verify they reach the target
Let's Practice with Examples!
Example 1: The Sweet Shop Challenge
At the candy store, you want to buy two treats that cost $1.50 together. Which two items could you choose?
Possible combinations:
- Gummy worms ($0.75) + Chocolate bar ($0.75) = $1.50
- Lollipop ($0.65) + Jelly beans ($0.85) = $1.50
- Bubble gum ($0.90) + Candy cane ($0.60) = $1.50
How about licorice ($0.80) + sour candy ($0.70) = $1.50? Great job finding combinations!
Example 2: Race Time Differences
In a running race, the difference between first and second place was 0.25 seconds. If the winner's time was 12.75 seconds, what could the second place time be?
Let's solve it:
12.75 - ? = 0.25 means ? = 12.75 - 0.25 = 12.50 seconds
If the difference was 0.30 seconds instead, the second place time would be 12.75 - 0.30 = 12.45 seconds. You're getting great at this!
Parent Tips 🌟
- Make it real: Use grocery receipts to practice adding decimal prices or calculate change from purchases.
- Decimal hopscotch: Draw a hopscotch with decimal numbers and have your child jump to numbers that add up to a target.
- Recipe math: When cooking, ask your child to adjust measurements by adding or subtracting decimal amounts.