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dsp73
3 years ago
9

The speed of the current is 7 mph. The boat travels three times slower against the current than with the current. What is the sp

eed of the boat in still water?
Mathematics
1 answer:
svlad2 [7]3 years ago
7 0
Let
x--------> <span>the speed of the boat in mph

we know that
</span>going upstream the speed is x-7 
<span>going downstream the speed is x+7 
</span>
let the distance be d 
<span>time to go upstream = d/(x-7) </span>
<span>time to go downstream = d/(x+7)
</span>
time going upstream is 3 times going downstream 
so
<span>3d/(x+7) = d/(x-7) </span>
<span>divide by d </span>
<span>3/(x+7) = 1/(x-7) </span>
<span>3x-21 = x+7 </span>
<span>2x = 28 </span>
<span>x = 14 
</span>
the answer is
<span>the speed of the boat in still water is 14 mph</span>
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The parabolic shape of the door is represented by y - 32 = -\frac{2}{49}\cdot x^{2}. (See attachment included below). Head must 15.652 inches away from the edge of the door.

Step-by-step explanation:

A parabola is represented by the following mathematical expression:

y - k = C \cdot (x-h)^{2}

Where:

h - Horizontal component of the vertix, measured in inches.

k - Vertical component of the vertix, measured in inches.

C - Parabola constant, dimensionless. (Where vertix is an absolute maximum when C < 0 or an absolute minimum when C > 0)

For the design of the door, the parabola must have an absolute maximum and x-intercepts must exist. The following information is required after considering symmetry:

V (x,y) = (0, 32) (Vertix)

A (x, y) = (-28, 0) (x-Intercept)

B (x,y) = (28. 0) (x-Intercept)

The following equation are constructed from the definition of a parabola:

0-32 = C \cdot (28 - 0)^{2}

-32 = 784\cdot C

C = -\frac{2}{49}

The parabolic shape of the door is represented by y - 32 = -\frac{2}{49}\cdot x^{2}. Now, the representation of the equation is included below as attachment.

At x = 0 inches and y = 22 inches, the distance from the edge of the door that head must observed to avoid being hit is:

y -32 = -\frac{2}{49} \cdot x^{2}

x^{2} = -\frac{49}{2}\cdot (y-32)

x = \sqrt{-\frac{49}{2}\cdot (y-32) }

If y = 22 inches, then x is:

x = \sqrt{-\frac{49}{2}\cdot (22-32)}

x = \pm 7\sqrt{5}\,in

x \approx \pm 15.652\,in

Head must 15.652 inches away from the edge of the door.

8 0
3 years ago
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