Group Activity Cards
Use groups of 3.
Materials: 15 index cards, scratch paper

"Interest"ing Investments 
In this activity, you will be calculating simple interest. Begin by copying the values below onto index cards, one per card. Shuffle the cards and place them face down on the table in three rows, five cards to each row.
Values to put on cards: 
p = $2000
p = $800
r = 8%
t = 1 year
t = 4 years 
p = $1200
r = 4%
r = 10%
t = 2 years
t = 5 years 
p = $1000
r = 5%
r = 15%
t = 3 years
t = 6 years 
On the cards are values for principal p, rate r, and time t. Your goal is to find two different combinations of values that are equal. For example, if you had a principle of $800, a rate of 15%, and a time of 6 years, the simple interest would equal 800 × 0.15 × 6 or $720. You would then need to find three different cards that would also give you a simple interest of $720, if such a set exists.
Each player should have a sheet of paper. Player 1 begins by turning over 1 card, recording the value on the card and placing it face down back on the table. Do not show the other players the value on the card. Player 2 then turns over one card and follows the same procedure. Play continues until a player has seen and recorded 2 sets of 3 cards that yield the same interest. On that player's next turn, he or she reveals his discovery and must correctly locate and turn over all six cards. If he or she can do so, that player wins the game. The other players should verify that these cards do result in the same amount of interest. If either the player cannot turn over the correct cards in one try or the cards used do not result in the same amount of interest, all six cards are flipped back over, that player looses his or her next turn and play continues.
(Hint: Try to keep track of which cards you have turned over on your paper so that you do not turn the same cards over twice.)
