Question

If a : b :: c : d is correct then is also correct.

• A. a : b : : d : c
• B. b : a : : c : d
• C. b : a : : d : c

Answer 1

The correct option is C b : a : : d : c

If a : b : : c : d then $\frac{a}{b}=\frac{c}{d}$
which can be written as $\frac{b}{a}=\frac{d}{c}$
i.e., b : a : : d : c
Therefore a : b : : c : d can be written as b : a : : d : c
This is called the invertendo property of proportions.