This tutorial covers Math in Focus Lesson 12.2 (Real-World Problems: Two-Step Problems). This takes the strategies learned in Lesson 12.1 and reapplies them to real-world problems requiring multiple steps.
In Student Book 3A, students have learned addition, subtraction, multiplication, and division of numbers up to 1,000. They have mastered the four operations using standard algorithms. Students have also learned how to use bar models to solve one-step and two-step real-world problems. Students have been taught to choose the correct operational concepts to solve real-world problems involving part-whole (in addition and subtraction), adding on, taking away, comparing, multiplying, and dividing. In order to solve real-world problems on measurements, students need to be proficient in conversions between the units of measures.
Drawing the various bar models allows students to think about how the given information in a problem is related. This understanding will lead students to eventually find a solution to any one- or two-step problem. The part-whole concept is one way of thinking about number relationships. In addition, the parts are put together to form a whole. In subtraction, the known part(s) and whole are used to find the missing part. In multiplication, the equal parts can be combined to find the whole (total). Similarly, in division, the whole can be divided up into equal parts.
In this video, we return to bar models to see how they can be used to solve problems with more than one step. To solve <i>one-step</i> real-world measurement problems, you can watch videos 3-10!
In this video, I use addition and a part-part-whole bar model to solve the first step. I use subtraction and a part-part-whole bar model to solve the final step.
The problem in this video requires a multiplication bar model for the first part, and a compare bar model (with addition) for the second part.
What's our first step in this problem? Using a part-part-whole bar model and subtraction to find the remaining amount of dried peas. For the second part, we need to use division to find the answer.
Boy, this one can be tricky! We have our "whole" in this problem, and we know how much is in each "part", but we don't know how many "parts" there are. First we'll have to use division to find that out, and then subtraction to solve the second part.
In our final video, you will use multiplication to solve part A. After you know how much juice is in all the glasses, you can use subtraction to find the answer to part B!