A. The half-life of carbon-14, an isotope used in archaeological dating, is 5730 years. What percentage of 14 6Cremains in a sample estimated to be

A. The half-life of carbon-14, an isotope used in archaeological dating, is 5730 years. What percentage of 14 6Cremains in a sample estimated to be 11,500 years old?

(Express your answer using one decimal place). ____ %?

B. A β-emitting radiation source gives 250 units of radiation at a distance of 2.8 m. At what distance does the radiation drop to one-tenth its original value?

(Express your answer using two significant figures). d= _____ m?