# 4.6 - Decimal Computation

The student will

a)  add and subtract decimals;* and

b)  solve single-step and multistep practical problems involving addition and subtraction with decimals.

*On the state assessment, items measuring this objective are assessed without the use of a calculator.

### BIG IDEAS

• We use measurement every day.We look at the temperature to see what we should wear to school. We measure ourselves to see if we are growing. What other things can you think of that we measure?

• We often use measurements of mass in Science to see how heavy an object is. We also measure liquids for experiments.

• Engineers use measurements daily when they are designing things such as bridges.

### UNDERSTANDING THE STANDARD

• Addition and subtraction of decimals may be explored, using a variety of models (e.g., 10-by-10 grids, number lines, money)
• The problem-solving process is enhanced when students create and solve their own practical problems and model problems using manipulatives and drawings.
• In problem solving, emphasis should be placed on thinking and reasoning rather than on key words.  Focusing on key words such as in all, altogether, difference, etc. encourages students to perform a particular operation rather than make sense of the context of the problem.  It prepares students to solve a very limited set of problems and often leads to incorrect solutions.
• The least number of steps necessary to solve a single-step problem is one.

### ESSENTIALS

The student will use problem solving, mathematical communication, mathematical reasoning, connections, and representations to

• Estimate sums and differences of decimals. (a)
• Add and subtract decimals through thousandths, using concrete materials, pictorial representations, and paper and pencil. (a)
• Solve single-step and multistep practical problems that involve adding and subtracting with decimals through thousandths. (b)

### KEY VOCABULARY

Updated: Aug 22, 2018