If a : b = 3 : 4, b : c = 4 : 7, then a + b + cc is equal to -

Answer: Option B

$$\begin{array}{rl}& =a:b=3:4\\ & =b:c=4:7\\ & \Rightarrow a:b:c=3:4:7\\ & \text{Let }a=3k,\\ & b=4k,\\ & c=7k.\\ & \text{Then,}\\ & \frac{a+b+c}{c}\\ & =\frac{3k+4k+7k}{7k}\\ & =\frac{14k}{7k}\\ & =2\end{array}$$