Unit 8: Problem Solving · Lesson 7
Problem Solving - Lesson 7
What this lesson is for
- Students will understand and practice Problem Solving - Lesson 7
- Students will solve problems related to this topic
Train up a child in the way he should go: and when he is old, he will not depart from it.
Proverbs 22:6
Multi-Step Problem Solving Strategies
Real-world problems rarely fit into a single operation. Multi-step problems require planning, organization, and multiple mathematical tools applied in sequence.
General Problem-Solving Framework (Polya's Method):
- Understand the problem: Read carefully; identify what's given, what's asked, what's unknown.
- Plan: Choose a strategy; identify what operations or formulas to use.
- Execute: Carry out the plan, showing all work.
- Check: Does the answer make sense? Does it satisfy the original conditions?
Common problem-solving strategies:
- Draw a picture or diagram
- Make a table or organized list
- Write an equation or inequality
- Work backwards
- Look for a pattern
- Break into smaller parts
Multi-step example 1: A T-shirt costs $15. A pair of jeans costs $45. You have $120 and need to buy shirts and one pair of jeans. How many shirts can you buy?
- Cost equation: 15s + 45 ≤ 120
- 15s ≤ 75; s ≤ 5 → at most 5 shirts
Multi-step example 2: Three siblings share $84. The oldest gets $12 more than the youngest. The middle child gets twice the youngest. Find each amount.
- Let y = youngest; middle = 2y; oldest = y + 12
- y + 2y + (y + 12) = 84 → 4y + 12 = 84 → 4y = 72 → y = 18
- Youngest: $18, Middle: $36, Oldest: $30 (Check: 18+36+30=84 ✓)
Multi-step example 3 (area + equation): A rectangular garden has perimeter 64 ft. Width is 3/4 of the length. Find area.
- 2l + 2w = 64; w = 3l/4
- 2l + 2(3l/4) = 64 → 2l + 1.5l = 64 → 3.5l = 64 → l ≈ 18.3 ft, w ≈ 13.7 ft
- Area ≈ 18.3 × 13.7 ≈ 250.7 sq ft
"Wisdom is the principal thing; therefore get wisdom: and with all thy getting get understanding." (Proverbs 4:7) — Multi-step problems demand wisdom — the ability to see the whole while managing the parts.
Guided practice
A family bought 3 bags of seed at $4 each and spent $15 total. How much was spent on other items? (Understand, plan, solve)
Show the steps and the answer
1. Understand: seed cost 3 × $4 = $12 2. Plan: subtract from total 3. Solve: $15 - $12 = $3
Answer: $3
Your chore list has 5 tasks. You complete 3 tasks in 20 minutes. At this rate, how long for all 5?
Show the steps and the answer
1. Find rate: 20 min ÷ 3 tasks = 6.67 min/task 2. Multiply: 6.67 × 5 = 33.33 minutes
Answer: 33.33 minutes (or about 33 1/3 minutes)
A recipe serves 4 people. You need to serve 10. The recipe calls for 2 cups flour. How much flour do you need?
Show the steps and the answer
1. Scale factor: 10 ÷ 4 = 2.5 2. Multiply: 2 × 2.5 = 5 cups
Answer: 5 cups
Homework
Complete the practice problems for Problem Solving - Lesson 7.
Note for the parent
Today's lesson covers Problem Solving - Lesson 7. Estimated time: 50 minutes. Encourage independent work but be available for questions.
The first three of this lesson's 10 questions
T-shirts $8, shorts $15. Spend exactly $74. Bought 2 shorts. How many T-shirts?
Show the answer
Answer: 5
Three consecutive even integers sum to 78. Smallest?
Show the answer
Answer: 24
Circle area = 78.5 sq ft. (π≈3.14) Circumference?
Show the answer
Answer: 31.4 ft
Another 7 questions follow in the lesson itself, each one graded the moment it is answered.