To find the scale David used for the drawing, we need to compare the length of the diving board in real life to its length in the drawing.
- The real-life length of the diving board is 20 feet.
- The length of the diving board in the drawing is 2 inches.
First, we need to convert 20 feet to inches since the drawing's measurement is in inches. There are 12 inches in a foot, so:
\[ 20 \text{ feet} = 20 \times 12 = 240 \text{ inches} \]
Now we have:
- Real-life length: 240 inches
- Drawing length: 2 inches
To find the scale, we can set up the relationship as follows:
\[ \text{Scale} = \frac{\text{Drawing Length}}{\text{Real-Life Length}} = \frac{2 \text{ inches}}{240 \text{ inches}} \]
This simplifies to:
\[ \text{Scale} = \frac{1}{120} \]
This means for every 1 inch in the drawing, it represents 120 inches in real life.
To convert this to feet (since there are 12 inches in a foot):
\[ 120 \text{ inches} = \frac{120}{12} = 10 \text{ feet} \]
Therefore, the scale is:
\[ \text{Scale} = 1 \text{ inch} : 10 \text{ feet} \]
Thus, David used a scale of 1 inch : 10 feet for the drawing.