Answer:
4 Minutes. (Approx, to the nearest minute)
Step-by-step explanation:
24.2% of 680 is: 164.56
164.56 * 4(Minutes) = 658.24
164.56 * 5(Minutes) = 822.8
So since it's rounded up, 5 minutes is too long because it would be long gone by then, and the next highest amount of minutes that it can decay for but not reach LESS than 10 grams left, is 4 minutes.
