A STORY OF UNITS Name Shenya Durde 1. Subtract. 1.7 – 0.8 = tenths – tenths = tenths Lesson 1 Date 2. Subtract vertically, showing all work. 8. 84637 – 2856 – 56077 14513 84637 -2856 56071
The Correct Answer and Explanation is:
1. Subtract:
1.7 – 0.8
Step-by-step:
- 1.7 has 7 tenths.
- 0.8 has 8 tenths.
- Since 7 tenths is less than 8 tenths, we need to regroup:
- Borrow 1 from the ones place in 1.7 (which becomes 0.7 + 1 = 1.7).
- This is the same as:
1.7 = 1.0 + 0.7 → becomes 0.9 + 0.17 (or 17 tenths – 8 tenths).
So:
- 17 tenths – 8 tenths = 9 tenths
Answer: 0.9
2. Subtract Vertically:
84637 – 2856
Set the numbers vertically:
markdownCopyEdit 84637
- 02856
-------
81781
Answer: 81,781
Explanation
Understanding subtraction—especially involving decimals or large numbers—requires a clear grasp of place value and regrouping.
In the first problem, 1.7 – 0.8, both numbers are written in decimal form and represent parts of wholes. Here, 1.7 means 1 whole and 7 tenths, while 0.8 means 8 tenths. When subtracting tenths, if the top number has fewer tenths (7 < 8), we must regroup from the whole number. We borrow 1 whole from the “1” in 1.7, converting it into 10 tenths, and then add the 7 tenths already there. This gives us 17 tenths. Subtracting 8 tenths from 17 tenths results in 9 tenths. Therefore, the final answer is 0.9.
The second problem involves subtracting multi-digit whole numbers. Writing numbers vertically ensures that each digit is correctly aligned by place value: units, tens, hundreds, thousands, and so on. Starting from the right (units place), we subtract digit by digit. If a digit in the top number is smaller than the digit below it, we regroup (borrow) from the next column. In this example, we subtract 2,856 from 84,637, which involves regrouping in a few places. After careful subtraction, the result is 81,781.
These problems reinforce important math concepts like place value, regrouping (borrowing), and decimal understanding. When students practice writing numbers in vertical form and show their work, they build strong computational skills and develop number sense. It’s also easier to spot and correct mistakes when the work is neatly organized step-by-step. Mastery of these foundational skills prepares students for more complex math operations in later grades.
