Question

Find the sub-duplicate ratio of 81:64?
A.8:9
B.4:9
C.9:8
D.7:8

Answer 1

Hint: Here, by the use of ratio concepts we will find the sub-duplicate ratio.

Let us consider the given ratio 81:64 be a: b, where $a = 81$ and $b = 64$. As, we know that if the ratio is given in the form of a: b then the sub-duplicate ratio can be written as $\sqrt a :\sqrt b $ .Therefore,
$ \Rightarrow \sqrt {81} :\sqrt {64} = 9:8$
Hence, the sub-duplicate ratio of 81:64 is 9:8.
Hence, the correct option for the given question is ‘C’.

Note: The sub-duplicate ratio of a: b is $\sqrt a :\sqrt b $ , whereas the duplicate ratio of a: b is ${a^2}:{b^2}$.