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tigry1 [53]
3 years ago
10

1)Sheyna drive to the lake and back. It took two hours less time to get there than it did to get back. The average speed on the

trip there was 60 mph. The average speed on the way back was 36 mph. How many hours did the trip there take?
Mathematics
1 answer:
ipn [44]3 years ago
8 0

Answer:

8 hours

Step-by-step explanation:

Given:

Sheyna drives to the lake with average speed of 60 mph and

v_1 = 60\ mph

Sheyna drives back from the lake with average speed of 36 mph

v_2 = 36\ mph

It took 2 hours less time to get there than it did to get back.

Let t_1 be the time taken to drive to lake.

Let t_2 be the time taken to drive back from lake.

t_2-t_1 = 2 hrs ..... (1)

To find:

Total time taken = ?

t_1+t_2 = ?

Solution:

Let D be the distance to lake.

Formula for time is given as:

Time =\dfrac{Distance}{Speed }

t_1 = \dfrac{D}{60}\ hrs

t_2 = \dfrac{D}{36}\ hrs

Putting in equation (1):

\dfrac{D}{36}-\dfrac{D}{60} = 2\\\Rightarrow \dfrac{5D-3D}{180} = 2\\\Rightarrow \dfrac{2D}{180} = 2\\\Rightarrow D = 180\ miles

So,

t_1 = \dfrac{180}{60}\ hrs = 3 \ hrs

t_2 = \dfrac{180}{36}\ hrs = 5\ hrs

So, the answer is:

t_1+t_2 = \bold{8\ hrs}

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Step-by-step explanation:

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Find an equation of the line containing the centers of the two circles whose equations are given below.
Anna35 [415]

Answer:

<h2><em>3y+x = -5</em></h2>

Step-by-step explanation:

The general equation of a circle is expressed as x²+y²+2gx+2fy+c = 0 with centre at C (-g, -f).

Given the equation of the circles x²+y²−2x+4y+1  =0  and x²+y²+4x+2y+4  =0, to  get the centre of both circles,<em> we will compare both equations with the general form of the equation above as shown;</em>

For the circle with equation x²+y²−2x+4y+1  =0:

2gx = -2x

2g = -2

Divide both sides by 2:

2g/2 = -2/2

g = -1

Also, 2fy = 4y

2f = 4

f = 2

The centre of the circle is (-(-1), -2) = (1, -2)

For the circle with equation x²+y²+4x+2y+4  =0:

2gx = 4x

2g = 4

Divide both sides by 2:

2g/2 = 4/2

g = 2

Also, 2fy = 2y

2f = 2

f = 1

The centre of the circle is (-2, -1)

Next is to find the equation of a line containing the two centres (1, -2) and (-2.-1).

The standard equation of a line is expressed as y = mx+c where;

m is the slope

c is the intercept

Slope m = Δy/Δx = y₂-y₁/x₂-x₁

from both centres, x₁= 1, y₁= -2, x₂ = -2 and y₂ = -1

m = -1-(-2)/-2-1

m = -1+2/-3

m = -1/3

The slope of the line is -1/3

To get the intercept c, we will substitute any of the points and the slope into the equation of the line above.

Substituting the point (-2, -1) and slope of -1/3 into the equation y = mx+c

-1 = -1/3(-2)+c

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Finally, we will substitute m = -1/3 and c = 05/3 into the equation y = mx+c.

y = -1/3 x + (-5/3)

y = -x/3-5/3

Multiply through by 3

3y = -x-5

3y+x = -5

<em>Hence the equation of the line containing the centers of the two circles is 3y+x = -5</em>

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