Question

Supposed that a certain ubstance has a half- life of 20 years.If there are presently 2500-milligrams of substance ,then the equation Q(t)=2500(2)−t/20 yields the amount remaining after t-years.How much remains after a. 81 years b.40 years c. 50 years

Answer 1

a.

$$Q(81)=2500\cdot 2^{-\frac{81}{20}}=151\ mg$$

b.

$$Q(40)=2500\cdot 2^{-\frac{40}{20}}=625\ mg$$

c.

$$Q(50)=2500\cdot 2^{-\frac{50}{20}}=442\ mg$$