Question

If 30 labourers working 7 hours a day can finish a peace of work in 18 days,how many labourers working 6 hours a day can finish it in 30 days

Answer 1

As 30 labours complete work in 18*7 hours=126 hours
let x labours nedded to complete work in =6*30=180hours

This is case of inverse variation,
So, 30*126=x*180
x=30*126/180=21 labours

Answer 2

21 labourers working 6 hours a day can finish the work in 30 days.

Given:

30 labours working 7 hours per day finishes peace of work in 18 days

To find:

Number of labours working 6 hours a day, finishes it in 30 days

Solution:

In 18 days working for 7 hours, the work is finished by = 30 labourers.

∴ In 18 days working for 1 hour, the work is finished by $=30 \times 7$ labourers.

∴ In 1 day working for 1 hour, the work is finished by $=30 \times 7 \times 18$labourers.

∴ In 1 day working for 6 hours, the work is finished by $=\frac{30 \times 7 \times 18}{6}$ labourers.

∴ In 30 days working for 6 hours, the work is finished by $=\frac{30 \times 7 \times 18}{6 \times 30}$ labourers.        

= 21 labourers.