UP Police Constable Exam Model Paper 4

Given:
4 taps fill an empty tank in 10 hours.
Concept used:
${\mathrm{M}}_1{\mathrm{D}}_1{\mathrm{H}}_1={\mathrm{M}}_2{\mathrm{D}}_2{\mathrm{H}}_2$
Where M is the number of Men, D is the number of Days and H is the number of Hours.
Explanation:
Let the number of taps needed to fill the tank in 5 hours be 'x'.
⇒ (4 taps) × 10 hours = (x taps) × 5 hours
⇒ x = 8 taps.
As there are already 4 taps,
⇒ The extra tap = (8 - 4)
⇒ 4
∴ The extra taps required to fill the tank in 5 hours are 4.