What is Deductive Reasoning?

Deductive reasoning is used to some degree in all problem solving. There are some problems that rely on very little besides deductive reasoning to arrive at a solution. We often call these "logical reasoning" problems and they must be worked through piece by piece to get to an answer. Frequently, these problems require little or no calculation to solve. Many people find it helpful to make a chart or diagram to keep track of solution parts as they are worked out.

How do you use deductive reasoning?

1. Decide exactly what it is you are trying to find out.
2. Identify all information you have available in the problem.
3. Design a way to record information you have as well as interrelationships between pieces of information.
4. Record all available information and use it to fill in blanks.
5. Look back to ensure each conclusion you make is justified based on the information you have.

Favourite Classes (click for animated solution) (click to download PowerPoint of solution)

At school, Kim, Terry, Robyn, and Dale all enjoy different subjects. Terry likes Phys. Ed. and always carries gym clothes. Neither Kim nor Dale particularly like Science class. Neither Terry nor Kim like math although Kim gets good marks in Math. Can you match these people with their favourites subjects - Math, Science, Phys. Ed., and English?

Who Does What? (click for solution)

When counting up activity points for the school awards ceremony, Pat noticed that many students were involved in similar sets of activities. There are 8 students who are members of the student council as well as being on the volleyball team, 7 students are in the choir as well as on playing on the volleyball team; and 5 students work on the yearbook staff as well as being members of the student council. How many more students play on the volleyball team than work on the yearbook staff?

Playing the Game (click for solution)

Rhonda had signed up for games at the school fun night. For the first set of games, seven other people were assigned to her group to make up four pairs of partners. Rhonda's group list showed her name as well as Darien, Anna, Jon, Christina, Joanne, Marcel, and Michael. When the games started, Darien and his partner were to the left of Marcel. Across from Darien was Rhonda, who was to the right of Jon. Darien's brother's partner, Christina, was across from Marcel. Joanne was not on Marcel's right. Can you name the four pairs of partners?