Question

Sodium-24 has a half-life of 15 h. How many hours is three half-lives?

a. 60 h
b. 45 h
c. 30 h
d. 15 h
e. 7.5 h

Answer 1

One half live = 15
So if we want three half lives we multiply 15 by 3
The number of hours in three half lives is 45

Answer 2

(B)

Step-by-step explanation:

If 1 half-life is 15 hrs, then 3 half-lives = 3×15 = 45

Therefore, there are 45 hrs in 3 half-lives (b)