In a certain organisation, 40% employees are matriculates, 50% of the remaining are graduates and the remaining 180 are post-graduates. What is the number of graduate employees ?

Answer: Option A

Let the total number of employees be x
Then,
(100 - 50)% of (100 - 40)% of x = 180
50% of 60% of x = 180
$$\begin{array}{rl}& \Rightarrow \left(\frac{50}{100}\times \frac{60}{100}\times x\right)=180\\ & \Rightarrow x=\left(\frac{180\times 10}{3}\right)\\ & \Rightarrow x=600\end{array}$$
∴ Number of graduate employees :
$$=$$ 50% of 60% of x
$$\begin{array}{rl}& =\left(\frac{50}{100}\times \frac{60}{100}\times 600\right)\\ & =180\end{array}$$