The time to plough a field varies directly as the area to be ploughed and inversely as the number of workers. If 8 workers can plought a 5 ha field in 6 houirs, how long will it take to plough a 10 ha field with 12 workers working at the same rate?
This is a problem on compound proportion.
Let the area to be ploughed be Quantity 1,
the time to plough a field be Quantity 2 and
the number of workers be Quantity 3.
Quantity1(area) Quantity2 (time) Quantity3(no.ofworkers)
10 x 12
According to the rule for solving compound proportions :
If quantity 1 and quantity 2 are directly related and quantity 2 and quantity 3 are inversely related, then we use the following rule:
Hence, it will take 8 hours to plough a 10 ha field with 12 workers working at the same rate
Please read the first line of the above table as:
Quantity1 Quantity2 Quantity3
5 6 8