Please i need someone to answer this for me. its urgent!!!!
A scientist is trying to determine the age of a rock layer in O points a canyon using Uranium-234, an isotope of Uranium. It has a half-life of about 2,000 years. There originally was 400 radioactive atoms of Uranium-234. If the rock layer tested has 100 radioactive atoms of U-234 left, how many half lives have passed AND how old is the rock layer?