Earth Science Unit 4 Day 2

Questions:

1. How do scientists know the age of rocks or fossils? (book or brain)
2. What is radioactive decay? (book)
3. Uranium-235 has a half-life of 700 million years. How long does it take a 100-gram sample of Uranium-235 to decay to a mass of 50 grams?

Answer choices for number 3:

	A. 350 million years B. 1,400 million years C. 235 million years D. 700 million years