On a vertical photograph of flat terrain, the scaled distance between two points is ab. Find the

Question:

On a vertical photograph of flat terrain, the scaled distance between two points is ab. Find the average photographic scale along ab if the measured length between the same line is AB on a map plotted at a scale of Smap for the following data.
(a) ab = 1.47 in.; AB = 3.55 in.; Smap = 1:6000
(b) ab = 41.53 mm; AB = 6.23 mm; Smap = 1:20,000