Question

210 men working 12 hours a day can finish ajob in 18 days. How many men are required to finish the job in 20 days working 14 hours a day? (3 marks)

Answer 1

Let the required number of men be x.

Hours	Day	Men
12	18	210
14	20	x

(1 mark)

More working hours ⇒ less men required.
∴ It is inverse proportion.
∴ Multiplying factor is 12/14
Also more number of days ⇒ less men
∴ It is an inverse proportion. (1 mark)

∴ Multiplying factor is 18/20
∴ x = 210×$\frac{12}{14}$×$\frac{18}{20}$=162 men
(1 mark)