HCU MCA 2013 Paper

(d) 6 technicians work in 1 h = $\frac{1}{10}$
11 am to 5 pm (6 h) work in 6 technicians = $\frac{1}{10}\times 6=\frac{3}{5}$
∴ Remaining work $=1-\frac{3}{5}=\frac{2}{5}$
∵ 1 technician added after 5 pm in each hour
∴ 1 technician in 1 h work $=\frac{1}{10}\times \frac{1}{6}=\frac{1}{60}$
∵5 am to 6 am (7 technicians) 1 h work = $\frac{7}{60}$
6 am to 7 am (8 technicians) 1 h work = $\frac{8}{60}$
and 7 am to 8 am (9 technicians) 1 h = $\frac{9}{60}$
Form work = $\frac{7}{60}+\frac{8}{60}+\frac{9}{60}=\frac{24}{60}=\frac{2}{5}$
∵Remaining work = form work
∴Total time = 8 pm