# Surf for More Math

## CHAPTER 8: ADDITION AND SUBTRACTION

**Lesson 10: Subtracting on a Place Value Mat **

Use these interactive activities to encourage students to have fun on the Web while learning about adding and subtracting two-digit numbers. Students can try these activities on their own or in pairs.

**Goals**

Model subtraction with base ten blocks and visual representations, and record the process symbolically.

Create and solve subtraction story problems.

[C, CN, PS, R]

**Instructions for Use**

**Base Ten Block Subtraction** lets students practise subtraction with and without regrouping.

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.