Display this problem:
A car can travel about 29 miles in one hour in traffic. How far can the car travel in three hours?
- What is important in this problem? (The car can travel about 29 miles per hour.)
- What is the problem asking you to solve? (How far the car can go in 3 hours)
- Can someone solve this problem? (29 is close to 30, so 30 miles per hour times 3 hours is about 90 miles.)
- How can we be sure this solution is reasonable? (Solve the problem using another strategy and compare the solutions. Use a mental-math strategy to solve the problem and compare the solutions. Use estimation.)
- What should you write down to show you checked to see if your solution is reasonable? (Show the steps of my other solution.)
Ask one or two students to show how they checked whether their solution to this car traveling problem was reasonable.
Have students work in pairs to solve the problems on the Multiplication Strategies pages in the Student Guide. In this set of word problems, students are asked to show how they know their answers are reasonable. Remind students to show the strategy they used to check their solutions for reasonableness.
When solving word problems, some students have trouble figuring out which numbers are important to the problem and what the problem is asking. Encourage students to draw a picture or write a sentence to help them figure out what the problem is asking and which numbers are important to the problem.
