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31 votes
You have 4,592 grams of a radioactive kind of scandium. How much will be left after 168 days if its half-life is 84 days?

User Mike Ratcliffe
by
2.7k points

2 Answers

12 votes
12 votes

Answer:

1,148

Explanation:

User Ullas Prabhakar
by
2.3k points
6 votes
6 votes

Answer:

1148 grams

Explanation:

You want to know the amount remaining of 4592 grams of scandium after 168 days if its half-life is 84 days.

Half-life

The half-life period is the time it takes for 1/2 of the amount to decay. After 84 days, the remaining amount is (4592 g)/2 = 2296 g. After 84 more days, a total of 168 days, the remaining amount is (2296 g)/2 = 1148 g.

1148 grams of the scandium will remain after 168 days.

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Additional comment

You can write an equation for the remaining amount:

remaining = (initial amount)·(1/2)^(t/(half-life))

remaining = 4592(1/2)^(t/84)

Then for t=168, this is ...

remaining = 4592(1/2)^(168/84) = 4592(1/2)^2 = 4592(1/4) = 1148

Units are grams and days.

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User Shawn Wilson
by
2.8k points
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