Uranium-238 has a half-life of 4.5 billion years. if earth is about 4.5 billion years old, which statement is true? a. in about 4.5 billion years, there will be the same amount of uranium-238 as there is today. b. about 4.5 billion years ago, there was half as much uranium-238 as there is today. c. about 4.5 billion years ago, there was twice as much uranium-238 as there is today. hell mm

C. About 4.5 billion years ago, there was twice as much uranium-238 as there is today.

Explanation: Radioactive decay process is a type of process in which a less stable nuclei decomposes to a stable nuclei by releasing some radiations or particles like alpha, beta particles or gamma-radiations.

Half life of a radioactive material is the time taken by the material to decompose to half of its original value.

Thus if Uranium-238 has a half-life of 4.5 billion years, it means it has decomposed to half of its original value and thus about 4.5 billion years ago, there was twice as much uranium-238 as there is today.

In next 4.5 billion years, i.e. after two half lives have passed, the amount of uranium will be one fourth of ts original value.

d₁ = displacement of tern from arctic to antarctic = 11000 miles

d₂ = displacement of tern from antarctic to arctic =   - 11000 miles

d = total displacement for the journey

total displacement for the journey is given as

d = d₁ + d₂

d = 11000 + (-11000)

d = 0 miles

t₁ = time of travel from arctic to antarctic = 3 months = 3 x 30 days = 90 days

t₂ = time of travel from antarctic to arctic = 3 months = 3 x 30 days = 90 days

t = total time of travel

total time of travel is given as

t = t₁ + t₂

t = 90 + 90

t = 180 days

average velocity is given as

average velocity = total displacement/ total time

v = d/t

v = 0/180

v = 0 miles/day