Please help! I don't understand!
Uranium-238 has a half-life of 4.5 billion years. Given that scientists estimate Earth's age to be 4.6 billion years, what is the most likely percentage of parent to daughter isotopes of this element currently existing on Earth?
10%
25%
50%
75%

Question

Please help! I don't understand! 
Uranium-238 has a half-life of 4.5 billion years. Given that scientists estimate Earth's age to be 4.6 billion years, what is the most likely percentage of parent to daughter isotopes of this element currently existing on Earth?
10% 
25%
50% 
75%

anonymous · Answer

i think this should be in physics/ chemistry

anonymous · Answer

but i guess u have to know what half- life is first

anonymous · Answer

oh ok

anonymous · Answer

i dont understand this stuff like at all

anonymous · Answer

well i don't exactly know how to calculate it but half life is the amount of time required for an element (for example) to fall to half its value as measured at the beginning of the time period, its like the rate of the element decays

anonymous · Answer

uranium is radioactive, it has a decaying rate

anonymous · Answer

isotope is like different forms of the same element, they will have same no. of protons but different no. of neutrons

twopointinfinity · Answer

yea this surely belongs in chemistry.