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sergejj [24]
2 years ago
6

Santos is a lifeguard and spots a drowning child 50 meters along the shore and 60 meters from the shore to the child. Santos run

s along the shore for a while and then jumps into the water and swims from there directly to the child. Santos can run at a rate of 4 meters per second and swim at a rate of 0.9 meters per second. How far along the shore should Santos run before jumping into the water in order to save the child
Mathematics
1 answer:
Amanda [17]2 years ago
7 0

Answer:

Santos should run approximately 36.145 meters along the shore

Step-by-step explanation:

The given parameters are;

The distance along the shore of the child = 50 meters

The distance from the shore of the child = 60 meters

The rate at which Santos can run = 4 m/s

The rate he can swim = 0.9 m/s

Let 'x' represent the distance he runs along the shore

We have;

The time he spends running on the shore, t₁ = x/4

The time he spends swimming, t₂ = (√(60² + (50 - x)²)/0.9

The total time, T = t₁ + t₂ = x/4 + (√(60² + (50 - x)²)/0.9

To find the maximum, we have;

dT/dx = 0 = d(x/4 + (√(60² + (50 - x)²)/0.9)/dx = 1/4 - (50 - x)/(0.9·(√(60² + (50 - x)²) = 0

1/4 - (50 - x)/(0.9·(√(60² + (50 - x)²) = 0

Simplifying using a graphing calculator gives;

\dfrac{x - 2000}{9} = \sqrt{x^2-100\cdot x+6,100}

1519·x² - 151900·x + 3505900 = 0

x = (151900 ± √((-151900)² - 4×1519×3505900))/(2 × 1519)

x ≈ 63.86 m or x ≈ 36.145 m

We note that the distance from a point x = 63.83 meters and 36.145 meters from where Santos spots the girl to the location of the girl are the same

Therefore, Santos should run approximately 36.145 meters along the shore before jumping into to the water in order to save the child

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Paul [167]

Answer:

1.60 ft^{2}

Step-by-step explanation:

Assuming that this is a cylindrical pipe, the area can be determined by applying the formula for calculating the area of a circle.

i.e Area = \pir^{2}

So that,

for the inner part of the pipe,

r = \frac{diameter}{2}

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 = 2.5 feet

Area of the inner part of the pipe = \pir^{2}

                                 = 3.14 x (2.5)^{2}

                                 = 19.625

Are of the inner part of the pipe is 19.63 ft^{2}.

Total diameter of the pipe = 5 + 0.2

                                           = 5.2 feet

r = \frac{5.2}{2}

 = 2.6 feet

Area of the pipe = \pir^{2}

                            = 3.14 x (2.6)^{2}

                            = 21.2264

Area of the pipe is 21.23 ft^{2}.

Thus the cross sectional area = Area of the pipe - Area of the inner part of the pipe

                                           = 21.2264 - 19.625

                                           = 1.6014

The cross sectional area of the cement pipe is 1.60 ft^{2}.

6 0
2 years ago
Need help with a math problem
Greeley [361]
The answer would be $159.85
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I forgot how to do this, can someone help me-
Artyom0805 [142]

Step-by-step explanation:

1) x/20 = -9

By cross multiplication,

x = -180

2) -168 = -14k

k = -168/-14

k = 12

3) -5m = -50

m = 10

4) -320 = -20n

n = 16

5) -4 = x - 5

x = 1

6) -6(-8 + n) = -54

42 - 6n = -54

-6n = -54 -52

6n = 106

n = 17.6

7) 3(x - 9) = -3

3x - 27 = -3

3x = 24

x = 8

8) 9k + 3 = -78

9k = -81

k = -9

9)4 + (n/4) = 8

By taking LCM,

16 + n/4 = 8

16 + n = 32

n = 16

10) -5r + 7 = -73

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r = 16

<em>Hope</em><em> </em><em>it</em><em> </em><em>helps</em><em>.</em>

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2 years ago
Solve the following system of equations <br> x^2+2y^2=59<br> 2x^2+y^2=43
aivan3 [116]

Answer: x = (-3,3), y = (-5,5)

Step-by-step explanation:

Add both of the equations together, for 3x^{2}+3y^{2} = 102. Now we can divide both sides by 3, gettingx^2+y^2=34. we subtract the first equation from our equation we just got, getting y^2=25 y= (5,-5). once we plug that in, we get 50+x^2 = 59, x^2 = 9 x = (-3,3)

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Dvinal [7]

Answer:

Step-by-step explanation:

Given

time taken by Carlos to cycle is t=0.5\ hr

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For 0.5 hr \approx 30\times 60=1800\ s

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Therefore Carlos might not be able to cover 6 miles with average speed of  16 ft/s

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for 0.5 hr

distance traveled

d=1800\times 18=32,400\ ft\approx 6.136

Therefore Carlos might be able to cover more than 6 miles with 18\ ft/s

5 0
3 years ago
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