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kobusy [5.1K]
3 years ago
15

ANSWER ASAP!! Find the area of a triangle with legs that are: 12 m, 15 m, and 9 m.

Mathematics
1 answer:
Setler79 [48]3 years ago
6 0

Answer:

<h2>54m²</h2>

Step-by-step explanation:

<h3>METHOD 1:</h3>

You can use the Heron's formula:

A=\sqrt{p(p-a)(p-b)(p-c)}

where

<em>p</em><em> - half of perimeter</em>

<em>a, b, c</em><em> - lengths of sides</em>

We have

a=12m;\ b=15m;\ c=9m

Calculate:

p=\dfrac{12+15+9}{2}=\dfrac{36}{2}=18\ (m)\\\\A=\sqrt{18(18-12)+(18-15)(18-9)}\\\\A=\sqrt{(18)(6)(3)(9)}\\\\A=\sqrt{2916}\\\\A=54\ (m^2)

<h3>METHOD 2:</h3>

Let's check that it is not a right triangle.

If the sum of the squares of the two shorter sides is equal to the square of the longest side, then this triangle is rectangular.

We have

9m < 12m

Check:

9^2+12^2=81+144=225\\15^2=225

This is a right trianglr wherew 9m and 12m are legs and 15m is a hypotenuse.

The formula of an area of a right triangle is:

A=\dfrac{ab}{2}

<em>a, b</em><em> - legs</em>

Substitute:

A=\dfrac{(9)(12)}{2}=\dfrac{108}{2}=54\ (m^2)

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A. The city we will use is Orlando, Florida, and we are going to examine its population growth from 2000 to 2010. According to the census the population of Orlando was 192,157 in 2000 and 238,300 in 2010. To examine this population growth period, we will use the standard population growth equation N_{t} =N _{0}e^{rt}
where:
N(t) is the population after t years
N_{0} is the initial population 
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r is the growth rate in decimal form 
e is the Euler's constant 
We now for our investigation that N(t)=238300, N_{0} =192157, and t=10; lets replace those values in our equation to find r:
238300=192157e^{10r}
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ln(e^{10r} )=ln( \frac{238300}{192157} )
r= \frac{ln( \frac{238300}{192157}) }{10}
r=0.022
Now lets multiply r by 100% to obtain our growth rate as a percentage:
(0.022)(100)=2.2%
We just show that Orlando's population has been growing at a rate of 2.2% from 2000 to 2010. Its population increased from 192,157 to 238,300 in ten years.

B. Here we will examine the population decline of Detroit, Michigan over a period of ten years: 2000 to 2010.
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Population in 2010: 713,777
We know from our investigation that N(t)=713777, N_{0} =951307, and t=10. Just like before, lets replace those values into our equation to find r:
713777=951307e^{10r}
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ln(e^{10r} )=ln( \frac{713777}{951307} )
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C. Final equation from point A: N(t)=192157e^{0.022t}.
Final equation from point B: N(t)=951307e^{-0.029t}
Similarities: Both have an initial population and use the same Euler's constant.
Differences: In the equation from point A the exponent is positive, which means that the function is growing; whereas, in equation from point B the exponent is negative, which means that the functions is decaying.

D. To find the year in which the population of Orlando will exceed the population of Detroit, we are going equate both equations N(t)=192157e^{0.022t} and N(t)=951307e^{-0.029t} and solve for t:
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E. Since we know that the population of Detroit as 2000 is 951307, twice that population will be 2(951307)=1902614. Now we can rewrite our equation as: N(t)=1902614e^{-0.029t}. The last thing we need to do is equate our Orlando's population growth equation with this new one and solve for t:
192157e^{0.022t} =1902614e^{-0.029t}
\frac{192157e^{0.022t} }{1902614e^{-0.029t} } =1
e^{0.051t} = \frac{1902614}{192157}
ln(e^{0.051t} )=ln( \frac{1902614}{192157} )
t= \frac{ln( \frac{1902614}{192157}) }{0.051}
t=44.95
We can conclude that after 45 years in 2045 the population of Orlando will exceed twice the population of Detroit. 

  
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