Algebra Balance: Unlike any other balance, this balance makes it possible to physically show that -1 < 0. Weights placed in the outer pans represent negative integers and those placed in the inner pans represent positive integers. Students use the balance to derive the rules for working with signed numbers, solving linear equations, building identities, and modeling systems of linear equations. Ideal for small group work, the sturdy 17" plastic balance comes with 4 plastic pans, a set of plastic weights, and 4 plastic canisters. Detailed instructional booklet included. Algebra Balance Activity Book: Written specifically for the Four-Pan Algebra Balance, this 64-page teacher resource book models how to use the balance to teach integers, additive inverses, and equivalent equations. Also shows how to solve equations in one or two variables and systems of equations. Teacher Notes and blackline masters included.