AThe half-life of an isotope is the amount of time it takes for half of the atoms in a sample to decay. If the half-life of a sample of uranium-234 is 2.5 * 10^5 years, it means that after 2.5 * 10^5 years, half of the atoms in the sample will have decayed.
If you want to know how long it will take for only one sixth of the original mass to be left, you can use the following formula:
t = (half-life) * log(2) / log(1/6)
Plugging in the values, we get:
t = (2.5 * 10^5 years) * log(2) / log(1/6)
This simplifies to:
t = 3.7 * 10^5 years
So it will take approximately 3.7 * 10^5 years for only one sixth of the original mass to be left.nswer: