A length measurement is meaningful when it is composed of repeated units of the same size, placed end to end with no gaps or overlaps, because the count then represents how many equal portions cover the length. If unit sizes differ, two counts cannot be compared directly: a longer unit produces a smaller count, while a shorter unit produces a larger count, even when measuring the same object; this understanding supports accurate comparison and later work with standard units.
To measure a length fairly, use units that are all the same size. Place them end to end with no gaps and no overlaps. Then the number of units tells how many equal pieces cover the object.
Example: Measure the same ribbon with blocks.
The counts are different because the unit sizes are different. A large block covers more length, so fewer large blocks are needed. A small block covers less length, so more small blocks are needed.
So, we cannot say the ribbon is longer because it measures blocks instead of blocks. The blocks are not the same size. To compare measurements, use equal-sized units each time.
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