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andrew-mc [135]
3 years ago
14

The function f(t) =16t 2 + 248 models the height f(t) in feet of a stone t seconds after it is dropped from the edge of a vertic

al cliff. How long will it take the stone to hit the ground? Round to the nearest hundredth of a second.
a. 0.25 seconds
Selected:b. 3.94 secondsThis answer is incorrect.
c. 5.57 seconds
d. 7.87 seconds
Mathematics
1 answer:
Hatshy [7]3 years ago
7 0

Answer:

The time it takes for the stone to reach the ground is 3.94 s. This answer is correct.

Step-by-step explanation:

I believe there's a mistake in the equation shown, the acceleration (number that multiplies t²) should be negative, since the stone is falling, therefore I'll answer assuming it's -16 instead of 16, otherwise there would be no real solution to the equation.

In order to calculate how long it'll take for the stone to hit the ground we must make f(t) = 0 and find the time "t" that makes the equation valid, so we have:

f(t) = -16t² + 248 = 0

-16t² = -248

t² = -248/(-16) = 15.5

t = sqrt(15.5) = 3.94

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<h3>Answer:  Approximately 23.0 cm</h3>

=====================================================

Work Shown:

a = 20.3

b = unknown

c = 30.7

Apply the pythagorean theorem to find b

a^2 + b^2 = c^2

(20.3)^2 + b^2 = (30.7)^2

412.09 + b^2 = 942.49

b^2 = 942.49-412.09

b^2 = 530.4

b = sqrt(530.4)

b = 23.0304146727757  value is approximate

b = 23.0

I rounded to one decimal place because the other values (20.3 and 30.7) were to one decimal place.

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Answer:

8

Step-by-step explanation:

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The volume of a cone is 37.7 cubic inches, and its height is 4 inches. What is the diameter of the base of the cone?
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4 years ago
A worker was paid a salary of $10,500 in 1985. Each year, a salary increase of 6% of the previous year's salary was awarded. How
Mazyrski [523]
Note that 6% converted to a decimal number is 6/100=0.06. Also note that 6% of a certain quantity x is 0.06x.

Here is how much the worker earned each year:


In the year 1985 the worker earned <span>$10,500. 

</span>In the year 1986 the worker earned $10,500 + 0.06($10,500). Factorizing $10,500, we can write this sum as:

                                            $10,500(1+0.06).



In the year 1987 the worker earned

$10,500(1+0.06) + 0.06[$10,500(1+0.06)].

Now we can factorize $10,500(1+0.06) and write the earnings as:

$10,500(1+0.06) [1+0.06]=$10,500(1.06)^2.


Similarly we can check that in the year 1987 the worker earned $10,500(1.06)^3, which makes the pattern clear. 


We can count that from the year 1985 to 1987 we had 2+1 salaries, so from 1985 to 2010 there are 2010-1985+1=26 salaries. This means that the total paid salaries are:

10,500+10,500(1.06)^1+10,500(1.06)^2+10,500(1.06)^3...10,500(1.06)^{26}.

Factorizing, we have

=10,500[1+1.06+(1.06)^2+(1.06)^3+...+(1.06)^{26}]=10,500\cdot[1+1.06+(1.06)^2+(1.06)^3+...+(1.06)^{26}]

We recognize the sum as the geometric sum with first term 1 and common ratio 1.06, applying the formula

\sum_{i=1}^{n} a_i= a(\frac{1-r^n}{1-r}) (where a is the first term and r is the common ratio) we have:

\sum_{i=1}^{26} a_i= 1(\frac{1-(1.06)^{26}}{1-1.06})= \frac{1-4.55}{-0.06}= 59.17.



Finally, multiplying 10,500 by 59.17 we have 621.285 ($).


The answer we found is very close to D. The difference can be explained by the accuracy of the values used in calculation, most important, in calculating (1.06)^{26}.


Answer: D



4 0
3 years ago
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