Let the speed of river be x km/hr down stream.
Time = Distance / speed
Since river flows downstream, speed of boat down stream = Speed of boat + speed of river = (15 + x).
Since river flows downstream, speed of boat upstream = Speed of boat - speed of river = (15 - x).
Time Upstream - Time Downstream = 75 minutes
Time Upstream = 45 / (15 - x)
Time Downstream = 45 / (15 + x)
75 minutes = 75/60 = 5/4 hours
Time Upstream - Time Downstream = 75 minutes = 5/4 hours
45 / (15 - x) - 45 / (15 + x) = 5/4 Divide both sides by 45
1 / (15 - x) - 1 / (15 + x) = (5/4)*(1/45)
1 / (15 - x) - 1 / (15 + x) = 1/36
((15 + x) - (15 -x)) / (15-x)(15+x) = 1/36
(15 +x - 15 +x) / (15-x)(15+x) = 1/36
2x / (15-x)(15+x) = 1/36
(15-x)(15+x) = 2x*36
(15-x)(15+x) = 72x
225 - x² = 72x
0 = x² + 72x -225
x² + 72x -225 = 0 This is a
quadratic function, use a calculator that can solve the function, by
inputting the function.
x = 3, or -75. Since we are solving for speed, we can not have negative values.
x = 3 is the only valid solution.
Speed of the river = 3 km/hr downstream.
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Answer:
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Step-by-step explanation:
there seems to be some missing info here.
<span>78.6 is a decimal number, you must name it with the whole part first and then the decimal part as part of tenths, hundredths or what it corresponds. In this case the whole part is 78 and the decimal part is 6/10 which is 6 tenths. Then, the number in words is sevety eight and six tenths.</span>
Answer:
The distance between point A and point B is 5 units
The volume of the spherical dome will be 12.9π cubic feet when the surface area of the dome is 13.924π.
<h3>What is the volume of the sphere?</h3>
The volume of the cone is the amount of quantity, which is obtained in the 3-dimensional space. The dome is the shape of a semi-sphere the volume of the dome will be half of the volume of the sphere.
Given that the Reunion Tower in Dallas, Texas, is topped by a spherical dome that has a surface area of approximately 13,924π square feet.
The volume of the dome will be calculated as below:-
SA = 13.924π
2πr² = 13.92π
r = √6.96
r = 2.63 feet
Volume = 2 / 3 πr³
Volume = ( 2 / 3 ) π ( 2.63)³
Volume = 12.24π cubic feet
Therefore, the volume of the spherical dome will be 12.9π cubic feet.
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