# Surf for More Math

## CHAPTER 8: ADDITION AND SUBTRACTION

**Lesson 7: Subtracting Two-Digit Numbers in Different Ways**

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.

**Goal**

Use personal strategies to subtract two-digit numbers with manipulatives.

[C, PS, R, V]

**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.

**Subtraction Machine** allows students to practise subtracting 2 one-digit numbers, subtracting 1 two-digit number and 1 one-digit number, and subtracting 2 two-digit numbers.

To use Subtraction Machine, select Level 2 for subtracting 2 one-digit numbers, and 1 two-digit number and 1 one-digit number. Enter your answer in the white box and click the button “Check my answer.” Your score is shown to the right. Select the Level for each question.

**Subtracting Practice** provides students extra practice subtracting 2 two-digit numbers.

To use Subtracting Practice, click on Lesson 13.4. Select the correct sum from the three choices. Click Check Your Answer. If your answer is correct, it will show your score and another question. If you are incorrect, you will be asked to try again. When you have completed several questions, click End the Quiz. Your final score is shown.