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arsen [322]
3 years ago
14

The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.

3 hours. If 1 gram of this isotope is present initially, how long will it take for 70% of the lead to decay? (Round your answer to two decimal places.)
Mathematics
1 answer:
Ksenya-84 [330]3 years ago
5 0

Answer:

5.73 hours

Step-by-step explanation:

70% decay means 30% remains

.3 = (1/2)^(t/3.3)

take the log of both sides

log.3 = t/3.3 * log1/2

Divide both sides by log 1/2

log.3 / log1/2 = t/3.3

use calculator

1.736965594166206 = t/3.3

multiply both sides by 3.3

5.73198646074848 = t

rounded

t = 5.73 hours

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Answer:

4 hours

Step-by-step explanation:

The distances and average speeds for the first two days driven are show below.

Step 1

We calculate the total distance covered in the first two days

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Hence:

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If the average speed on the third day is 50 miles per hour,

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