 # Surf for More Math

## Lesson 9 - Strategies for Subtracting

Use these interactive activities to encourage students to have fun on the Web while learning about strategies for subtracting. Students can try these activities on their own or in pairs.

### Goal

Subtract a 1-digit number from a 2-digit number.

### Instructions for Use

Base Ten Block Subtraction lets students practice subtracting a 1-digit number to a 2-digit number.

To use Base Ten Block Subtraction, drag a red block over a blue block of the same size to cancel the red block out. When you have more red blocks than blue blocks in a column, drag a larger blue block from the column to the left into the column that has more red blocks than blue blocks. The block will automatically break up into smaller blocks. You can now cancel out the remaining red blocks in that column. Once you have cancelled out all of the red blocks in all of the columns, the subtraction solution will appear in the area on the far left.

Number Line Arithmetic lets students visualize subtracting numbers on a number line.

To use Number Line Arithmetic, select the "-" button at the bottom of the screen. Click the "Go" button under the mathematical problem. Animated arcs represent the problem. Click the "New Problem" button and a new problem will be displayed.

Interactive Calculator allows students to subtract a 1-digit number from a 2-digit number, and display them on a 100 chart.

To use Interactive Calculator, start by clicking a 2-digit number on the interactive calculator. This number will appear in the calculator window. Click the "-"button on the calculator, and then press a 1-digit number. Click the "=" button on the calculator.   