COURSE 2 LESSON 1-5
Using a Problem-Solving Plan
A carpenter makes and sells small tables. Some tables have
three legs, and some have four legs. Last month the carpenter made
20 tables. There were a total of 74 legs on these tables. How many
tables had four legs?
Determine what you know and what you need to find out.
Each table has three or four legs. On 20 tables, 74 total legs are counted.
You want to find out how many of the 20 tables had four legs.
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COURSE 2 LESSON 1-5
Using a Problem-Solving Plan
(continued)
Choose a strategy.
The total number of tables has to equal 20. Since the number of possibilities
isn’t very large, you can try, check, and revise to find out how many tables
had four legs. Make a table to organize your work.
Choose a possible answer to test. For example, you could start with 10
three-leg tables and 10 four-leg tables.
Tables With
3 Legs
Tables With
4 Legs
Total Number
of Legs
Result of Test
10
10
(10 • 3) + (10 • 4) = 70
low
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COURSE 2 LESSON 1-5
Using a Problem-Solving Plan
(continued)
Since the result of the first test is too low, you need to increase the total
number of legs. So increase the number of four-leg tables and decrease the
number of three-leg tables. Keep testing and revising until you get 74 legs.
Tables With
3 Legs
Tables With
4 Legs
Total Number
of Legs
Result of Test
10
10
(10 • 3) + (10 • 4) = 70
low
9
11
(9 • 3) + (11 • 4) = 71
low
7
13
(7 • 3) + (13 • 4) = 73
low
6
14
(6 • 3) + (14 • 4) = 74
Fourteen tables had four legs.
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COURSE 2 LESSON 1-5
Using a Problem-Solving Plan
(continued)
Think about how you solved the problem. To check whether the answer is
reasonable, look at the problem in another way. Use logical reasoning.
All 20 tables have at least three legs. That accounts for 60 of the 74 legs.
Since 74 – 60 = 14, 14 tables must have four legs. The answer is
reasonable and checks.
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COURSE 2 LESSON 1-5
Using a Problem-Solving Plan
Use the problem-solving plan.
Maria and Lila mounted an insect collection for life science class. There
were 75 insects in the collection, and Lila mounted 29 more insects than
Maria. How many insects did each mount?
Lila, 52; Maria, 23
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