**Technology objective: **Students will use the TI-34 calculators to find
the greatest common factor of a pair of numbers.

**Lesson: **After a discussion of greatest common factor, ask the students if they can figure out how to use the TI-34 calculator to find the greatest common factor of a set of numbers. Put various suggestions on the board. Next, explain to the students
how to use the TI-34 calculator to find the greatest common factor of a pair of
numbers. They can do this by entering one number in the place of the numerator
and one number in place of the denominator. Have them try to find the greatest
common factor of 45 and 60. Have them enter the smaller number in for the
numerator, 45, and the bigger number in for the denominator, 60. When the
press enter, the calculator will simplify the fraction they entered. Ask the
class to figure out what was factored out of the numerator and denominator.
(This serves as a great mental exercise.) Once they have figured that number out, they
know the greatest common factor. Have them try to find the greatest common
factor of any two random numbers. Also discuss what happens when you enter two
prime numbers. This can serve as a wonderful introduction to fractions.

**Reinforcement:**

*Game*

This game was found in the 1992 Yearbook ** Calculators in Mathematics
Education **in the article

25, 60, 45, 15, 10, 80, 48, 64, 36, 24, 65, 99, 27, 16, 42, 81, 75, 25, 200, 300, 500, 600, 800, 900, 360, 480, 640, 550, 270, 120, 144, 625, 525, 648, 864, and 468.

*GCF game*

1) Decide who plays first. Play then alternates.

2) On your turn, your opponent chooses an uncovered number on the grid.

3) You then choose a second uncovered number on the grid. Cover both choices.

4) Your score for the round is the GCF of the two numbers.

5) The winner is the player with the greatest cumulative score after five rounds.