Lesson Objectives
- Solve word problems using decimals with all four operations.
- Apply rounding and estimation to simplify calculations.
- Interpret real-world problems and identify the correct operation.
- Check answers for reasonableness using estimation and rounding.
Introduction
Decimal word problems appear in many real-world scenarios like money, measurements, and distances. Understanding how to apply decimal operations accurately is key to solving them efficiently.
Examples
Example 1: Addition
Sarah bought 3.75 meters of ribbon and 2.6 meters of fabric. How many meters did she buy in total? 3.75 + 2.6 = 6.35 meters
Example 2: Subtraction
A tank contains 25.5 liters of water. If 7.2 liters are used, how much water remains? 25.5 − 7.2 = 18.3 liters
Example 3: Multiplication
Each bottle contains 1.25 liters of juice. If a store sells 8 bottles, how many liters in total? 1.25 × 8 = 10 liters
Example 4: Division
10.5 meters of rope is divided equally among 3 students. How much does each get? 10.5 ÷ 3 = 3.5 meters per student
Practice Problems
- A baker uses 2.75 kg of flour for one batch and 3.4 kg for another. How much flour is used in total?
- A car travels 125.6 miles and then 78.4 miles. How far in total?
- A ribbon of 12.6 m is cut into 4 equal pieces. Length of each piece?
- Estimate 24.7 ÷ 3 using rounding before calculating.
Summary
Decimal word problems require applying addition, subtraction, multiplication, and division in context. Use rounding and estimation to check answers for accuracy and reasonableness.