A water tank can be emptied by using one pump for 4 hours. A second, smaller pump can empty the tank in 7 hour?

Larger pump empties tank in 4 hours

So in 1 hour it does 1/4 of the tank

Smaller pump empties tank in 7 hours

So in 1 hour it empties 1/7 of the tank

Time given to empty tank = 3 hours

In 3 hours larger pump does 3/4 of the tank

Balance = 1/4 of the tank to be done by smaller pump

= 7/4 = 1.75 hours

ANSWER smaller pump to be started at 2.15 P.M.

4pm - 1 pm is 3 hrs.

In 3 hours pump 1 will empty 3/4 of the tank.

Pump 2 needs to empty 1/4 of the tank and we need to find how long that will take.

The common denominator is 28 so pump 2 will need to empty 7/28 of the tank at a rate of 4/28 per hour or 1 hour and 45 minutes.

4 pm minus 1 hour and 45 minutes is 2:15 pm

!.0.5 is the minimum salinity for mudskippers. i could make an intermediate salinity help interior the 5 gallon, enable them to get used to that till they consume at decrease salinity, and then placed them interior the greater suitable tank.