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Word problems
Learning Outcome: •
Solve a word problem by forming an algebraic equation involving two operations
Overview This word problem requires the skill of forming an algebraic equation involving two operations. Go through the word problem using the 4-step Understand-Plan-Answer-Check process. Have students read the word problem and identify the key information. This will help them understand the word problem and interpret it correctly.
1. Understand the problem. −
Explain to students that they need to find the unknown y , which is the number of eggs in each carton at first.
2. Plan what to do. −
Point out to students that they can draw a part-whole bar model and form an algebraic equation in terms of y to solve the problem.
3. Work out the Answer . −
Draw 5 equal units as shown in the first bar model in the thought bubble. Label each unit as ‘ y ’. − Explain to students that this bar model represents the 5 cartons of eggs that the baker had at first. − Next, draw a part-whole bar model as shown in the second bar model in the thought bubble. − Guide students to see that since the baker used 12 eggs and had 18 eggs left, we split the bar into 2 parts to show this. The shorter part of the bar represents the 12 eggs that were used, and the longer part represents the 18 eggs that were left. − Using the part-whole bar model as a guide, have a student write the algebraic equation, 5 y – 12 = 18, on the board. − Guide students in solving the equation using the balance method. Elicit responses from students for each step. − Have students see that y = 6 and get them to conclude that there were 6 eggs in each carton at first. Guide students to check their answers by seeing if they get 18 eggs left when they substitute 6 for y in the expression 5 y – 12. Since 5 × 6 = 30, and 30 – 12 = 18, conclude that the answer is correct.
4. Check whether your answer is correct. −
Grade 7 I Teacher’s Guide 61
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