The table shows the amount of radioactive element remaining in a sample over a period of time. Radioactive Decay Rate

Amount of Radioactive Sample

(grams) Time(years)

56.0 - 0

47.1 - 400

39.6 - 800

33.3 - 1,200

28 - 1,600

Part 1: What is the half-life of the element? Explain how you determined this.

Part 2: How long would it take 312 g of the sample to decay to 9.75 grams? Show your work or explain your answer.