# Decimal Subtraction

Decimal subtraction is one of a series of Labs to help you understand and learn to use decimals. I think you will find it fun because it uses random numbers and it will help you visualize decimal operations. Take a look at Decimal Addition and Decimal Multiplication and Decimal Division. Remember like all of our spreadsheets you can look at and change the rules to try different things.

Multiplication is often thought of as repeated addition. By building a times table by using a repeated addition rule you will have a fun practice of the multiplication facts, and you will learn to build rules in spreadsheets. Rules let you program spreadsheets to do remarkable things like make the multiplication table in just a couple of easy steps.

# More Number Lines

We use rules to build new numberlines. For example we can start in the middle and go both forward or backward using adding and subtracting rules. You can even generate and experiment with negative numbers by subtracting below 0. As you build numberlines on spreadsheets you are building them in your mind. And by thinking of numberlines in terms of rules you are getting ready for algebra.

# Build a House

Spreadsheets with their natural grid make a great, though not entirely flexible, platform for architectural design and for working with shapes. Build a house introduces students to using spreadsheets to create floor plans and to measure area. Most spreadsheets have amazing graphic flexibility. You may want to encourage students to use spreadsheets for art. Here is an incredible example: http://www.spoon-tamago.com/2013/05/28/tatsuo-horiuchi-excel-spreadsheet-artist/