In order to sign a purchase and sale contract with customers, Wang Laohan estimated the total quality of fish in his fish pond, and fished out 100 for the first time, weighing 184 kg.

①100 ÷10100 =1000 (pieces).

② The average mass of tagged fish is184 ÷100 =1.84 kg.

The mass of 20 marked fish is 1.84× 20 = 36.8kg,

The average mass of fish is (184+416-36.8) ∴ (100+200-20) ≈ 2.011kg.

That is1000× 2.011= 2011kg.

Answer: Wang Laohan's fish pond is estimated to have 1000 fish, and the total mass is estimated to be 20 1 1 kg.