Answer:
The scale factor is 21. For every inch on the model, there are 21 on the real tower.
Explanation:
The 70-foot tower is 840 inches tall. The model she made is 40 inches tall.
70 * 12 = 840
We can divide 840 by 40 to get the scale factor per inch.
840 / 40 = 21
That means, for every inch on the model, there are 21 inches on the tower.