To 1 significant digit, how much Coumarin (in grams) would a 70 kg (154lb) student have to ingest to reach the LD50?

2 * 10 g

Step-by-step explanation:

The lethal dose 50 (LD50) of Coumarin is 293 mg/kg body mass. The amount of Coumarin that a 70 kg student would have to ingest to reach the LD50 is:

70 kg body mass * (293 mg/kg body mass) = 20510 mg

1 gram is equal to 1000 milligrams. The mass (in grams) corresponding to 20510 milligrams is:

20510 mg * (1 g / 1000 mg) = 20.51 g ≈ 2 * 10 g