O lvl E Maths: Ratio Rate Proportion

RI 1998 Sec 3 EOY Q2

3 men, working 8 hours a day, can finish a job in 6 days. How many days would it take 2 men working 9 hours a day to complete the same job, assuming that they work at the same rate?

*************************

Answer:

Total number of man-hours when 3 men are working 8 hours a day for 6 days
= (3 * 8 * 6) man-hours

Days taken to complete when 2 men are working 9 hours a day
= (3 * 8 * 6) / (2 * 9)
= 8 days