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Caffeine has a half-life of approximately 5 hours. Mohammed drinks a cup of coffee that contains 350 mg of caffeine. How long will it take until there is less than 15 mg of caffeine left in his bloodstream? Give your answer to 1 decimal place.

User Birol
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Final answer:

It will take approximately 26.9 hours until there is less than 15 mg of caffeine left in Mohammed's bloodstream.

Step-by-step explanation:

The half-life of caffeine is approximately 5 hours. To calculate the time it takes for there to be less than 15 mg of caffeine left in Mohammed's bloodstream, we can use the equation:

C(t) = C0 * (1/2)^(t/h)

where C(t) is the concentration of caffeine at time t, C0 is the initial concentration of caffeine (350 mg), t is the time passed, and h is the half-life of caffeine (5 hours).

Let's solve for t:

15 = 350 * (1/2)^(t/5)

Dividing both sides by 350:

0.042857 = (1/2)^(t/5)

Taking the logarithm of both sides:

log(0.042857) = log[(1/2)^(t/5)]

Using the logarithmic property, we can bring t/5 down:

log(0.042857) = (t/5) * log(1/2)

Dividing both sides by log(1/2):

t/5 = log(0.042857) / log(1/2)

Multiply both sides by 5:

t = 5 * (log(0.042857) / log(1/2))

Plugging this into a calculator, the value for t is approximately 26.9 hours.

User Alyawn
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