Finding the difference between two lengths means determining how much longer one whole-number measurement is than another when both are expressed in the same unit, by interpreting the gap as subtraction. A number line, ruler scale, or bar model can represent the endpoints and the distance between them, supporting the distinction between the difference and the total length; this work does not include unit conversions, fractional measurements, or more complex measures.
When two lengths use the same unit, the difference tells how much longer one length is than the other. Find the difference by subtracting the shorter length from the longer length.
Example: A ribbon is centimeters long. A string is centimeters long. How much longer is the ribbon?
The ribbon is centimeters longer than the string.
The difference is the gap between the two lengths, not the total length when they are put together.
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