Answer is Option B = 5/7
Explanation:
A scale factor is a number which scales, or multiplies, some quantity. In the equation y = Kx, K is the scale factor for x. K is also the coefficient of x, and may be called the constant of proportionality of y to x.
For big pictures or maps, images should be drawn without affecting the shape in a small paper. Hence dimension of x is reduced to y with constant proporiton k which is scale factor
Here we find that original length of PC = 21
In image P'C = 15
Hence scale factor=15/21 = 5/7
