Make sure POINTS is the active data frame. Using the Layout toolbar, zoom in on the scale bar. What number appears at its left end? ___________. Right end? ___________. Flip to the Data View. Now select the other Zoom In tool—the one on the Tools toolbar. Drag a box around the points that make the “P.” Go back into Layout View and look at the scale bar. Now what are the numbers at the ends of the scale bar? ___________ ___________. Now select Zoom Whole Page. Notice that you have made the “P” in the POINTS data frame much larger, and that the change was reflected in the legend of the scale bar. Flip back to the Data View and zoom to the some_points layer. As you return to the Layout View you can see that the scale bar has changed back to about the original number. Click on Zoom Whole Page. In the Layout View, select the POINTS data frame. Drag the box larger. The box becomes larger but the contents stay the same size. Move the borders of the box back. Now use the Zoom In tool on the Tools toolbar—making the ”A” larger. Note that the scale on the Standard toolbar changes. Also the scale on the map legend changes. The scale bar dynamically keeps up with the true map scale. It may not appear so on the screen, but it will be pretty close to right when the map is printed out or when you select the Zoom To 100% (1:1) button. Source.