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Lesson ⁦3-8⁩: Problem-Solving Investigation: Choose the Best Strategy

Math · Fifth Grade, Primary · Unit 3: Multiplication · First Semester

A 10-question quiz; after every question you'll see the right answer with an explanation.
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What will you learn in this lesson?

Students choose the best strategy for each problem from the ones they have learned, such as working backward, guess and check, drawing a picture, and looking for a pattern, then apply it and check the solution.

  • Understands the problem and identifies what it requires
  • Plans by choosing a suitable strategy: work backward, guess and check, draw a picture, or look for a pattern
  • Solves the problem using the chosen strategy
  • Checks that the solution is correct and reasonable

💡 Tip: Ask yourself: Do I know the end and need the beginning? Work backward. Do the numbers repeat regularly? Look for a pattern. Are there places and distances? Draw a picture.

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Worked examples from the Problem-Solving Investigation: Choose the Best Strategy lesson questions

What is the most suitable strategy for solving the problem: "I thought of a number, added 12 to it, then multiplied the result by 2 and got 40. What is the number?"
  • Work backward
  • Draw a picture
  • Look for a pattern
  • Make a frequency table
✓ Work backward
We know the final result and the operations that were done, so we start from the end and use inverse operations.
I thought of a number, added 12 to it, then multiplied the result by 2 and got 40. What is the number?
  • 8
  • 28
  • 32
  • 14
✓ 8
We work backward: 40 ÷ 2 = 20, then 20 − 12 = 8. Check: (8 + 12) × 2 = 40.
Show more examples (3)
A farmer plants a tree every 4 meters along a row that is 20 meters long, starting at the beginning and ending at the end. How many trees does he plant?
  • 6
  • 5
  • 4
  • 80
✓ 6
We draw a picture: 20 meters has 5 spaces of 4 meters each, and the number of trees is 5 + 1 = 6.
What is the next number in the pattern: 3, 7, 11, 15, ...?
  • 19
  • 18
  • 20
  • 17
✓ 19
The pattern increases by 4 each time: 15 + 4 = 19.
The sum of the ages of two sisters is 20 years, and the older one is 4 years older than the younger one. How old is the older sister?
  • 12 years
  • 8 years
  • 16 years
  • 10 years
✓ 12 years
By guess and check: 12 + 8 = 20 and 12 − 8 = 4.

FAQ about the Problem-Solving Investigation: Choose the Best Strategy lesson

What strategy fits this problem: I thought of a number, added 12, then multiplied the result by 2 and got 40?

Work backward, because we know the final result: 40 ÷ 2 = 20, then 20 − 12 = 8, so the number is 8.

What is the next number in the pattern 3, 7, 11, 15?

The pattern increases by 4 each time, so the next number is 15 + 4 = 19.

How do I study the lesson Problem-Solving Investigation: Choose the Best Strategy and test myself on it?

Start the lesson quiz on Study with Ghada: 10 questions from the Math Fifth Grade, Primary question bank. After each answer you'll see the right answer with an explanation, and any questions you miss move to “Review my mistakes” until you master them.

Are Study with Ghada quizzes free and aligned with the curriculum?

Yes, completely free. They're built on the Math - Grade 5 - Semester 1 lessons in the same order as the book, and every question is reviewed and approved by a teacher before students see it.

Unit 3 lessons: Multiplication

⁦3-1⁩ Multiplication Patterns ⁦3-2⁩ Distributive Property ⁦3-3⁩ Estimate Products ⁦3-4⁩ Multiply by a One-Digit Number ⁦3-5⁩ Problem-Solving Strategy: Draw a Picture ⁦3-6⁩ Multiply by a Two-Digit Number ⁦3-7⁩ Multiplication Properties All Math Fifth Grade, Primary lessons →
← ⁦3-7⁩ Multiplication Properties ⁦4-1⁩ Division Patterns →