What is the width of one of the smaller rectangles if the entire rectangle has a width of 21?

To determine the width of one of the smaller rectangles when the entire rectangle has a width of 21, it is essential to consider how the large rectangle might be divided into smaller sections. In many cases, specifically if the smaller rectangles are of equal width, the total width can be evenly divided.

If option C, which is 7, is chosen, then it implies that several smaller rectangles (each being 7 units wide) fit perfectly into the total width of 21. In this scenario, three smaller rectangles would line up next to each other, as 7 + 7 + 7 equals 21.

This method of division aligns with the typical approach in geometry where a larger shape is composed of smaller, uniformly sized shapes.

In contrast, the other options do not divide the total width of 21 evenly into smaller rectangles. For instance, choosing 3 would only allow for seven sections (3 x 7 = 21) but does not maintain the idea of equal-width smaller rectangles if not all sections are the same. Therefore, selecting 7 as the width ensures that the division is uniform and fits perfectly within the total width of 21.