Adding and Subtracting Decimals with Few Non-Zero Digits


Activity #1

Practice Addition and Subtraction.

In the following exercise, you are going to to practice on finding the sum and difference of decimal numbers. Follow the instructions below.

  • Attempt the problems on paper before checking the answers.​
  • Check the Hint boxes to see the explanations.​
  • Click the white square box at the left bottom for a new problem.
  • Practice with harder problems by moving the slider to the right. You might have to high light it and use the forward arrow key on your key board.

  • Without actually performing the calculations below, match each addition to the numbers on the right.

Activity #2

Add by Creating Base-ten Blocks.

The applet below has tools that create each of the base-ten blocks. You need to decide the value of each block before you begin. Read and follow the instructions below to learn how to create blocks.

  • Select a Block tool, and then click on the screen to place it.
  • Click on the Move tool (the arrow) when you are done choosing blocks.
  • Subtract by deleting with the delete tool (the trash can), not by crossing out.

  • Then, compute each sum below by drawing base-ten diagrams on the applet to help you.

(1.) 0.11 + 0.005

(2.) 0.209 + 0.01

(3.) 10.2 + 1.1456

(4.) 0.2 + 0.05

Activity #3

Subtract by Creating Base Ten Blocks.

In the previous activity, you learnt how to create blocks using the base-ten block applet. below are a set of questions for you to subtract using base-ten blocks.

  • Find each difference. If you get stuck, you can use the applet below to represent each expression and find its value.
  • Explain how you got your answer in each case.

(a.) 0.3 – 0.05

(b.) 2.1 – 0.4

(c.) 1.03 – 0.06

(d.) 0.02 – 0.007

Challenge #1

Answer True or False. Explain your reasoning in each case.

Challenge #2

Andre and Jada drew base-ten diagrams to represent . Andre drew 11 small rectangles. Jada drew only two figures: a square and a small rectangle.

(1.) If both students represented the sum correctly, what value does each small rectangle represent?

(2.) What value does each square represent?

(3.) Describe a diagram that could represent the sum . OR draw it in the applet below.

  • Draw a diagram using the applet below that could represent the sum .

Challenge #3

Quiz Time