Rounding the number $0.456$ to one decimal place results in $0.5$.

When rounding to one decimal place, it’s essential to examine the digit in the second decimal place, as it determines whether to round up or down. In this instance, the number is $0.456$. The first decimal place contains the digit $4$, while the second decimal place has the digit $5$. According to standard rounding conventions, if the second decimal digit is $5$ or greater, we round up the first decimal digit by one. Conversely, if it is $4$ or less, we retain the first decimal digit as it is.

In this example, since the second decimal place is $5$, we round up. Consequently, the $4$ in the first decimal place increases to $5$. Therefore, $0.456$ rounded to one decimal place is $0.5$. This rounding method strikes a balance between accuracy and simplicity, making numbers easier to work with.

Rounding is a valuable skill applicable in various areas of mathematics and everyday situations. It simplifies numbers, enhancing comprehensibility and ease of use, particularly when handling large datasets or performing complex calculations. Remember, the crucial step is to evaluate the digit immediately following the place to which you are rounding; this will guide your decision on whether to round up or down.