well type o blood is really rare you can find o well i don;t know but A and B is not That rare so if you cross it 50% of people has A Blood and 80% of people has B Blood and only 2% of people has O Blood
What percent of potassium-40 remains undecayed in a rock that is 3.9 billion years old? The 3.9 billion year old rock has undergone three half-lives (3.9 divided by 1.3 = 3). After 3 half-lives, 12.5% of the potassium-40 remains undecayed.
