Uranium-235 has a half-life of 700 million years. How many years will it take Uranium-235 to decay to 1/8 of its original mass?

2.1 billion years

Explanation:

The half-life of an element refers to the amount of time it would take for half of its mass to decay.

In 700 million years, Uranium - 235 will be 1/2 of its original mass.

If divided by 2, the 1/2 becomes 1/4 which is the proportion of the original mass the Uranium would get to after another 700 million years.

Dividing by another would get the Uranium-235 to 1/8 of its original value and would take another 700 million years.

Total time taken:

= 700 + 700 + 700

= 2,100 million years

= 2.1 billion years