Lesson 3
Adding and Subtracting Decimals with Few NonZero Digits
Let’s add and subtract decimals.
Problem 1
Here is a baseten diagram that represents 1.13. Use the diagram to find \(1.13  0.46\).
Explain or show your reasoning.
Problem 2
Compute the following sums. If you get stuck, consider drawing baseten diagrams.

\(0.027 + 0.004\)

\(0.203 + 0.01\)

\(1.2 + 0.145\)
Problem 3
A student said we cannot subtract 1.97 from 20 because 1.97 has two decimal digits and 20 has none. Do you agree with him? Explain or show your reasoning.
Problem 4
Decide which calculation shows the correct way to find \(0.30.006\) and explain your reasoning.
Problem 5
Complete the calculations so that each shows the correct difference.
Problem 6
The school store sells pencils for $0.30 each, hats for $14.50 each, and binders for $3.20 each. Elena would like to buy 3 pencils, a hat, and 2 binders. She estimated that the cost will be less than $20.
 Do you agree with her estimate? Explain your reasoning.
 Estimate the number of pencils could she buy with $5. Explain or show your reasoning.
Problem 7
A rectangular prism measures \(7\frac{1}{2}\) cm by 12 cm by \(15\frac{1}{2}\) cm.
 Calculate the number of cubes with edge length \(\frac{1}{2}\) cm that fit in this prism.
 What is the volume of the prism in \(\text{cm}^3\)? Show your reasoning. If you are stuck, think about how many cubes with \(\frac12\)cm edge lengths fit into \(1\text{ cm}^3\).
Problem 8
At a constant speed, a car travels 75 miles in 60 minutes. How far does the car travel in 18 minutes? If you get stuck, consider using the table.
minutes  distance in miles 

60  75 
6  
18 