This week, your student will add and subtract numbers using what they know about the meaning of the digits. In earlier grades, your student learned that the 2 in 207.5 represents 2 hundreds, the 7 represents 7 ones, and the 5 represents 5 tenths. We add and subtract the digits that correspond to the same units like hundreds or tenths. For example, to find
Any time we add digits and the sum is greater than 10, we can “bundle” 10 of them into the next higher unit. For example,
To add whole numbers and decimal numbers, we can arrange
Here is a task to try with your student:
Find the value of
Solution: 7.308. Sample explanation: there are 8 thousandths from 0.768. Next, the 4 hundredths from 6.54 and 6 hundredths from 0.768 combined make 1 tenth. Together with the 5 tenths from 6.54 and the 7 tenths from 0.768 this is 13 tenths total or 1 and 3 tenths. In total, there are 7 ones, 3 tenths, no hundredths, and 8 thousandths.
This week, your student will multiply decimals. There are a few ways we can multiply two decimals such as
Here is a task to try with your student:
Find
Solution: 4.64. The area of the rectangle (or the sum of the partial products) is:
This week, your student will divide whole numbers and decimals. We can think about division as breaking apart a number into equal-size groups.
For example, consider
Everyone gets
The calculation on the right shows different intermediate steps, but the quotient is the same. This approach is called the partial quotients method for dividing.
Here is a task to try with your student:
Here is how Jada found
Solution
IM 6–8 Math was originally developed by Open Up Resources and authored by Illustrative Mathematics, and is copyright 2017-2019 by Open Up Resources. It is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0). OUR's 6–8 Math Curriculum is available at https://openupresources.org/math-curriculum/.