A wave will travel only as long as it has energy to carry. The energy makes a wave travel and it will stop traveling as soon as the energy is dissipated.
Set this up as
10 = 40 (1/2)t/28
and solve for t in years.
10/40 = (1/2)t/28
log(0.25) = (t/28) log(0.5)
t = 28 log(0.25) / log(0.5) years = 56 years
Test the answer:
56 years = 2(28 years) = 2 half-lives, so the remaining amount should be 1/2 of 1/2 of the initial amount, i.e. 1/4 of the initial amount, and 10 mg = 1/4 of 40 mg.
The hubble telescope thing
Answer:
Studies point out that almost 70 percent of the South American continent is made up of hydrographic basins with naturally navigable rivers, which provide real opportunities to become a strategic factor that favors the transportation of merchandise, economic revitalization, and in general, a comprehensive development
Explanation:
