Use the following to answer questions:
Refer to the diagram below, showing the decay of a radioactive substance.
-How long will it take for only 12.5 percent of the substance to remain?

Question

Use the following to answer questions:
Refer to the diagram below, showing the decay of a radioactive substance. 
-How long will it take for only 12.5 percent of the substance to remain?

Quizplus · Accepted Answer

To find out how long it will take for only 12.5% of the substance to remain, we need to find the half-life of the substance. The half-life is the time it takes for half of the original substance to decay. Looking at the graph, we can see that the half-life is approximately 210,000 years. This means that every 210,000 years, half of the substance will decay. To find out how long it will take for only 12.5% to remain, we need to find out how many half-lives it will take to get to that point.

Starting with 100%, we need to go down to 12.5%, which is a decrease of 87.5%. We can calculate the number of half-lives needed by dividing 87.5% by 50% (since each half-life is a reduction of 50%).

87.5% / 50% = 1.75

So, it will take 1.75 half-lives for the substance to decrease to 12.5%. Multiplying this by the half-life of 210,000 years, we get:

1.75 x 210,000 = 367,500

Therefore, it will take approximately 367,500 years for only 12.5% of the substance to remain. The closest option to this is option C, 420,000 years.

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