Ronald and Elan are working on an assignment. Ronald takes 6 hours to type 32 pages on a computer, while Elan takes 5 hours to type 40 pages. How much time will they take, working together on two different computers to type an assignment of 110 pages ?

Answer: Option C

Number of pages typed by Ronald in 1 hour
$$\begin{array}{rl}& =\frac{32}{6}\\ & =\frac{16}{3}\end{array}$$
Number of pages typed by Elan in 1 hour
$$\begin{array}{rl}& =\frac{40}{5}\\ & =8\end{array}$$
Number of pages typed by both in 1 hour
$$\begin{array}{rl}& =\left(\frac{16}{3}+8\right)\\ & =\frac{40}{3}\end{array}$$
∴Time taken by both to type 110 pages
$$\begin{array}{rl}& \text{ = }\left(100\times \frac{3}{40}\right)\text{hours}\\ & =8\frac{1}{4}\text{hours}\\ & =\text{8 hours 15 minutes}\end{array}$$