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Lisa [10]
3 years ago
5

If a snowball melts so that its surface area decreases at a rate of 3 cm2/min, find the rate at which the diameter decreases whe

n the diameter is 10 cm.
Mathematics
1 answer:
tensa zangetsu [6.8K]3 years ago
5 0

Answer:

The diameter decreases at a rate of -0.0477 cm/min when it is 10 cm.

Step-by-step explanation:

Surface area of a snowball:

A snowball has a spheric format, which means that it's surface area is given by:

A = 4\pi r^2

In which r is the radius, which is half the diameter. In function of the diameter, the area is given by:

A = 4\pi(\frac{d}{2})^2 = \pi d^2

Solving the question:

To solve this question, we have to implicitly derivate the area in function of t. So

\frac{dA}{dt} = 2d\pi\frac{dd}{dt}

Snowball melts so that its surface area decreases at a rate of 3 cm2/min

This means that \frac{dA}{dt} = -3

Find the rate at which the diameter decreases when the diameter is 10 cm.

This is \frac{dd}{dt} when d = 10. So

\frac{dA}{dt} = 2d\pi\frac{dd}{dt}

-3 = 20\pi\frac{dd}{dt}

\frac{dd}{dt} = -\frac{3}{20\pi}

\frac{dd}{dt} = -0.0477

The diameter decreases at a rate of -0.0477 cm/min when it is 10 cm.

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3 years ago
Janet worked 3 hours more than David and 7 hours less than Kate. David earned $7.50 per hour, Janet earned $6 per hour, and Kate
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We want to write and solve a system of equations to see how much each person earns.

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Let's define:

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The information is:

<em>"Janet worked 3 hours more than David and 7 hours less than Kate"</em>

From this we can write:

J = D + 3

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We can rewrite the first and second equations to get:

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Now we can replace these two in the other equation to get:

$9*(J + 7) = $27 + ($7.50)*(J - 3)+ $6*J

Now we can solve this for J:

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And with:

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If you want to learn more, you can read:

brainly.com/question/9351049

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