If A pump can take 5 hrs to fill a 50 l of tank then how much time to take to fill a 75 liters of tank for the same pump? 

Correct option is (D) \(7\,\frac{1}{2}\) hrs \(\because\) Time taken to fill a \(50\,l\) of tank = 5 hours \(\therefore\) Time taken to fill a \(75\,l\) of tank \(=\frac5{50}\times75\;hours\) \(=\frac{75}{10}\;hours\) = 7.5 hours = 7 hours + \(\frac12\) hours = \(7\frac12\) hours

Correct option is (C) 96 Time = 1 hr 20 minutes = (60+20) minutes = 80 minutes Total work done by 6 pumps in 1 hr 20 minutes \(=6\times80=480.\) Let 5 pumps take time to fill the...

Correct option is (D) 3 Distance covered by car by travelling 60 kmph in 4 hours = speed \(\times\) time \(=60\times4\) = 240 km When car travels at 80 kmph then time by the car \(=\frac{Distance}{Speed}\) \(=\frac{240}{80}\) =...

Correct option is (A) 24 Number of required workers \(=\frac{15\times48}{30}\) \(=\frac{48}2\) = 24

Correct option is (A) \(112\frac12\,km/hrs\) Distance covered by train in \(2\frac12\) hrs = speed \(\times\) time = 90 \(\times\) \(2\frac12\) km = 90 \(\times\) \(\frac52\) km = 45 \(\times\) 5 km = 225 km \(\therefore\) Speed required to covered same distance (225 km) in 2 hours \(=\frac{Distance}{Time}\) \(=\frac{225}2\,km/hrs\) \(=112\frac{1}2\,km/hrs\)

Correct Answer - 12 hours

Correct Answer - C Consider, the filling of tank as a positive work and emptying the tank as negative work.