1. Solving Problems by Inductive Reasoning
Section 1-1
Solving Problems by Inductive Reasoning

2. Solving Problems by Inductive Reasoning
Characteristics of Inductive and Deductive Reasoning
Pitfalls of Inductive Reasoning

3. Characteristics of Inductive and Deductive Reasoning
Inductive Reasoning Draw a general conclusion (a conjecture) from repeated observations of specific examples. There is no assurance that the observed conjecture is always true. Deductive Reasoning Apply general principles to specific examples.

4. Example: determine the type of reasoning
Determine whether the reasoning is an example of deductive or inductive reasoning.
All math teachers have a great sense of humor. Patrick is a math teacher. Therefore, Patrick must have a great sense of humor.
Solution
Because the reasoning goes from general to specific, deductive reasoning was used.

5. Example: predict the product of two numbers
Use the list of equations and inductive reasoning to predict the next multiplication fact in the list:
37 × 3 = × 6 = 222
37 × 9 = × 12 = 444
Solution
37 × 15 = 555

6. Example: predicting the next number in a sequence
Use inductive reasoning to determine the probable next number in the list below.
2, 9, 16, 23, 30
Solution
Each number in the list is obtained by adding 7 to the previous number.
The probable next number is = 37.

7. Pitfalls of Inductive Reasoning
One can not be sure about a conjecture until a general relationship has been proven. One counterexample is sufficient to make the conjecture false.

8. Example: pitfalls of inductive reasoning
We concluded that the probable next number in the list 2, 9, 16, 23, 30 is 37. If the list 2, 9, 16, 23, 30 actually represents the dates of Mondays in June, then the date of the Monday after June 30 is July 7 (see the figure on the next slide). The next number on the list would then be 7, not 37.

9. Example: pitfalls of inductive reasoning

10. Example: use deductive reasoning
Find the length of the hypotenuse in a right triangle with legs 3 and 4. Use the Pythagorean Theorem: c 2 = a 2 + b 2, where c is the hypotenuse and a and b are legs.
Solution
c 2 =
c 2 = = 25
c = 5