This unit will focus on Addition, Subtraction, Multiplication, and Division of Decimals. Within that focus, we will also cover how to use rounding to estimate sums and differences.
The assessment is currently scheduled for around October 17th.
We had a quick review of rounding and a lesson on rounding decimals. However, we don't have much class time for practicing rounding numbers, so here is a game to help students practice rounding whole numbers and decimals: Soccer Math
The assessment is currently scheduled for around October 17th.
We had a quick review of rounding and a lesson on rounding decimals. However, we don't have much class time for practicing rounding numbers, so here is a game to help students practice rounding whole numbers and decimals: Soccer Math
Addition
The students have already been practicing the basic addition and subtraction on their Daily 5 reviews, and they covered it in 4th grade as well. With addition, they simply have to remember to line up the decimal points on each addend and to place it in the sum- otherwise, nothing changes from regular addition! (examples from CoolMath.com)
Practice Game: Hoop Shoot
Practice Game: Hoop Shoot
Students will need to be able to use a hundreds grid to add decimals. You can find some examples here.
Subtraction
With subtraction, some of the problems will work the same as subtraction in past year, as long as students remember to line up the decimals and place them in the answer. However, in some problems, students will have to add a decimal point to a whole number, or have to add additional zeroes in order to regroup.
Rounding to Estimate
With Rounding to Estimate, students will need to round each number to the nearest whole number BEFORE adding or subtracting.
Example 1:
Example 2:
Multiplication
In this section, students will be expected to multiply decimals. More specifically, they will expected to:
Below is an example from CoolMath.com of how to multiply a decimal by a whole number. A more detailed explanation from CoolMath.com can be found here. A video tutorial from Math Playground can be found here.
- Multiply any decimal by 10, 100, or 1000
- Determine the placement of the decimal point using estimation
- Multiply a decimal (up to hundredths) by a whole number
- Multiply a decimal by a decimal
Below is an example from CoolMath.com of how to multiply a decimal by a whole number. A more detailed explanation from CoolMath.com can be found here. A video tutorial from Math Playground can be found here.
Below is a model for multiplying decimals. This is the first year students will be required to learn this strategy, but I don't anticipate it to be a problem!
Division
If the students remember how to do regular long division, then dividing decimals is simple! You can go to the CoolMath.com page here to see the details and for more examples, but examples of the expectations for our students is below.
Below is an example of how to divide with a decimal in the divisor. You can find an animation of this skill here.
Dividing by Powers of Ten
To divide by 10, 100, or 1000, simply move the decimal point to the left as many spaces as there are zeros. It is a shortcut to using long division or repeated subtraction. Here is a video with examples:
(YouTube video by Education Galaxy. Direct link here.)
Estimation & Decimal Placement
Students can use estimation to determine the placement of a decimal in an answer. For example, in the problem 11.95 ÷ 1.9 = 6 2 8 9, where should the decimal be placed? If you round to 12 and 2, you can use 12 ÷ 2 = 6 to determine that it should be placed between the 6 and 2 to make 11.95 ÷ 1.9 = 6 . 2 8 9.