Draw a plain scale to show yards for a map whose scale is 4 inches : 1 mile.

Solution

Scale 4 inches: 1 mile

4 inches on the map represent =1 = 1760 yards

1 inch on the map represents = 1760/4 yards

6 inches on the map represent = $equals 1760 over 4 space straight x space 6 space equals space 2640 space yards$

But 2640 yards is not a round number. Select a round number of 3000 yards.

1760 yards are represented by = 4 inches

3000 yards are represented by

$space equals space 4 over 1760 space straight x space 3000 space inches equals space 1 over 440 space straight x space 3000 space inches equals 75 over 11 space inches space equals space 6.8 space inches$

Construction: Draw a line 6.8 inches long. Divide it into 6 equal parts each showing 500 yards. Sub-divide the left-hand part into 5 equal divisions. Each will show 100 yards.