# Adding and Subtracting Decimals with Many Non-Zero Digits

Warmup

Clare bought a photo for 17 cents and paid with a \$5 bill. Here are three ways to write the subtraction calculation.

(2.) Explain how you know.

Activity #1

Add and Subtract Decimals with many non-zero digits.

For this activity, you will need a sheet of paper and pencil/pen. Calculators are not recommended because, it is our aim to see that you master the process of adding/subtracting numbers by first aligning them into columns before proceeding with the operation. Follow the instructions below to get started. • Read the problem and write down the digits into columns. Make sure they are properly aligned.
• Perform the required operation (Addition/subtraction.)​
• Uncheck the boxes before you click on . This step is important in that, you do not work from answer to problem.

Activity #2

Subtract Decimal Numbers Using Blocks. • Use the ten-blocks in the applet below to find the value of each expression.

(1.) 11.3 – 9.5

(2.) 318.8 – 94.63

(3.) 0.02 – 0.0116

• Write the missing digits in the calculations below so that the value of each sum or difference is correct.

• Complete the calculations so that each shows the correct sum.

• Use the applet below to complete the missing information.

For every 9 customers, the chef prepares 2 loaves of bread. Here is double number line showing varying numbers of customers and the loaves prepared.

• The same information is shown on a table. Complete the missing information.
• Use either representation to answer these questions.

(1.) How many loaves are needed for 63 customers?

(2.) How many customers are there if the chef prepares 20 loaves?

(3.) How much of a loaf is prepared for each customer?

Activity #3

Practice by Creating numbers Using Base ten Blocks. • Use the applets below to provide answers to the following questions;

(1.) Use base-ten blocks to build 174.

Explain how you know you correctly built the number 174.

(2.) Use base ten blocks to build 238.

(3.) Build any number less than 500.

(4.) What number did you build? How do you know?

Challenge #1

Subtract the numbers in the applet below. verify your answer by checking the “Answer” box. Then click “Problem” to request for a new one. Practice as much as time allows you. Switch to “Add” the numbers to keep practicing.

Challenge #2

In a cryptarithmetic puzzle, the digits 0-9 are represented using the first 10 letters of the alphabet. Use your understanding of decimal addition to determine which digits go with the letters A, B, C, D, E, F, G, H, I, and J.

Challenge #3

For each subtraction problem, mark the correct calculation. use the pen tool located under .