Question

A machine that cost £35,000 is operated 8 hours a day in a 5-day week but one hour each day is used for test purposes. For use of the machine there are three scales of charges, the first at the rate of £5 an hour for private use, the second at £15 an hour for research work and the third at £40 an hour for commercial work. It is estimated that the number of hours charged at the first, second and third rates are in ratios 4:2:1. What percentage of total receipts do receipts from commercial work represent?

Answer 1

Total ratio = 4 + 2 + 1 = 7 

Unit of one ratio = 35/7 = 5
So, Number of Hours for commercial work = 5(1) = 5

Total receipt = 20 * 5  +  15 * 10  + 1 * 40 = 100 + 150 + 40 = 290
Commercial work receipt = 1 * 40 = 40

So, % = 40/290 * 100

= 400/29
= 13.79%

In short, Your Answer would be: 13.79%

Hope this helps!