If 3.0 g of Sr-90 in a rock sample remained in 1999,approximately
40. If 3.0 g of Sr-90 in a rock sample remained in 1999,
how many grams of Sr-90 were
present in the original rock sample in 1943? (1) 9.0 g
(2) 6.0 g (3) 3.0 g (4) 12 g