If A : B = 7 : 9 and B : C = 5 : 4, then A : B : C is -

Answer: Option C

$$\begin{array}{rl}& =\text{A}:\text{B}=7:9\text{and}\\ & \text{B}:\text{C}=5:4\\ & =\left(5\times \frac{9}{5}\right):\left(4\times \frac{9}{5}\right)\\ & =9:\frac{36}{5}.\\ & \Rightarrow \text{A}:\text{B}:\text{C}=7:9:\frac{36}{5}\\ & =35:45:36.\end{array}$$