It is assumed that each pumping pipe pumps water per hour 1 serving.

24 pipes, pumping 24×6= 144 copies in 6 hours.

2 1 tube, 2 1×8= 168 copies in 8 hours.

The difference between 168- 144 =24 copies.

It is the water that enters the water inlet pipe within 8-6=2 hours.

The average water inflow is 1 hour, and 24÷2= 12.

Water can enter 12×6=72 parts within 6 hours.

Row again,

24 pipelines, pumping water every 6 hours 144 copies,

72 of them are new water in these six hours.

The remaining 144-72=72 is the raw water in the pond.

For 16 tubes,

In which 12 root pumps 12 fresh water every hour.

And 16- 12=4, which is the original water in the pumping pool.

It takes 72÷4= 18 hours to drain.