I used this lab to work with students on using a triple beam balance and metric ruler. I scale could also be used. The premise of this lab is to determine is a vending machine can be tricked by using metal washers instead of coins. Students find various measurements of those objects and come to a conclusion of how a vending machine works and why they can't be tricked. This lab takes 2 40-minute periods to complete.
You will need for each partnership:
Triple Beam Balance or Scale
1 penny, 1 nickel, 1 dime, 1 quarter, 1 half dollar, 1 dollar coin, 1 dollar bills and metal washers in sizes approximate to the size of the actual coins.