Question

Starting with 189 grams of uranium-238, after one half life has gone by, how many grams of uranium-238 will remain?

Answer 1

95.5 g

Explanation:

To solve half life problems we need the formula:
`"mass after (n) number of half lives"= (1/2)^n *"original mass"`

In your example only one half time passed, therefore:
`mass= (1/2)^1 * "original mass" = 1/2 * 189 "grams"= 95.5 g`