When adding, subtracting, or comparing decimal numbers, aligning the decimal points is essential. This ensures each place value is correctly lined up, preventing errors in your calculations. Decimals represent fractions whose denominators are powers of ten. Thus, the digit just after the decimal point is in the tenths place, the next in the hundredths place, and so forth.
To illustrate, think about adding 0.6 mg two times. You would place the numbers in such a way that the decimal points in each number align vertically:
By aligning the decimal points, you make sure you're adding tenths to tenths, which gives 1.2 in this scenario. Always double-check that your decimal points are aligned properly, as even a small misalignment can lead to big mistakes, especially in critical fields like medicine.