SOLUTION: The half life of a certain isotope is 8.5. If we we have a sample of 10 ounces of isotope show much of it will remain after one full day. One of 4 choices is the answer. 0.28 ou

Question 1197601: The half life of a certain isotope is 8.5. If we we have a sample of 10 ounces of isotope show much of it will remain after one full day. One of 4 choices is the answer. 0.28 ounces, 0
14 ounces, 1.41 ounces, or 2.83 ounces. Which answer is correct?
Found 4 solutions by josgarithmetic, ikleyn, greenestamps, ewatrrr:
Answer by josgarithmetic(39618)   (Show Source): You can put this solution on YOUR website!
Half life of 8.5, what? Time unit needed. Either days or hours most likely

8.5 HOURS, the half life.

1.41 ounces after 24 hours.

Answer by ikleyn(52790)   (Show Source): You can put this solution on YOUR website!
.

Without pointing half-life dimension (year, day, hour, minute etc.) this problem MAKES no SENSE,
and the question can not be answered properly.

Answer by greenestamps(13200)   (Show Source): You can put this solution on YOUR website!

Obviously the post is made carelessly, without a time unit on the half life. But given the answer choices, we can determine logically what those units are.

We start with 10 ounces, and the answer choices for the amounts remaining after 1 day (24 hours) are between 0.28 and 2.83 ounces. Since the amount of the isotope decreases by 1/2 every half life, 24 hours has to be approximately 3 to 4 half lives; that means the given half life of "8.5" is in fact 8.5 hours.

So the number of half lives is 24/8.5, and the amount remaining after 24 hours is, to 2 decimal places, is

Answer by ewatrrr(24785)   (Show Source): You can put this solution on YOUR website!
ln(.5)/8.5 = -.0815
Q(24) = 10e^(- .0815*24) = 1.41 ounces
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