Answer:
a) 
b) The pollution level at 4 o'clock in the afternoon is of 280 parts per million.
Step-by-step explanation:
The pollution level in the center of a city at 6 am is 30 parts per million and it grows in linear fashion by 25 parts per million every hour.
This means that the pollution in t hours after 6 am is given by:
, which is the answer to question a.
b. The pollution level at 4 o'clock in the afternoon
4 in the afternoon is 10 hours after 6 am, so this is y(10).
The pollution level at 4 o'clock in the afternoon is of 280 parts per million.
First we will evaluate: ( substitution: u = x² - y², du = - 2 y dy )
=
( than plug in x and 0 )
=
=
= 1/3 x³ ( then another integration )
= 1/3 * 1/4 =
1/12
Answer:
Step-by-step explanation:
Usually, this wording means the decrease is proportional to the current price, characteristic of an exponential function.
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The decay factor is 1-(decay rate), so is 1-0.15 = 0.85. After 3 years, the value has been multiplied by this factor 3 times:
$50×0.85³ ≈ $30.71 . . . . cost in 3 years
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<em>Comment on percent per year</em>
Less often, the indicated decrease is intended to be <em>that percentage of the original price</em>. The result is that the price decreases by a constant amount each year, a linear decrease. This condition most often arises in conjunction with figuring depreciation in value for tax or accounting purposes.
The upshot is that you always need to be careful to understand what the base of a percentage is intended to be.
Use a calculator and it gives you the answer right away
