An ancient was analyzed and found to contain C-14 that had decayed for nearly 2 half lives. Approximately how old is the bone

11,460 years

Explanation:

The age of the bone would be approximately 11,460 years.

The half-life of a substance represents the time required for one-half of an amount of that substance to decay or disintegrate.

The half-life of C-14 is approximately 5,730 years. If the ancient bone had decayed for 2 half-lives it means that the bone had decayed for 5,730 x 2 = 11,460 years.

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom