Aboat traveled 100 miles downstream and back the trip downstream took five hours the trip back to 10 hours what is the speed of the boat in stillwater what is the speed of the current

Step-by-step explanation:

The relation between time, speed, and distance is ...

  speed = distance/time

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The speed downstream is ...

  downstream speed = (100 mi)/(5 h) = 20 mi/h

The speed upstream is ...

  upstream speed = (100 mi)/(10 h) = 10 mi/h

The boat's speed in still water is the average of these:

  boat speed = ((downstream speed) + (upstream speed))/2 = (20 +10)/2 mi/h

  boat speed = 15 mi/h

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The speed of the current is the difference between the travel speed and the boat speed:

  current speed = downstream speed - boat speed

  = (20 mi/h) - (15 mi/h)

  current speed = 5 mi/h

256π units²   (answer b)

step-by-step explanation:

the formula for the surface area of a sphere of radius r

is             a = 4πr²

and so, if r = 8 units, then the surface area is:

a = 4π(8 units)² = 256π units²   (answer b)

b. 1.25 hr

step-by-step explanation:

if you have a constant speed of 60 mph, then you have a ratio between 60 mi. to 1 hr. dividing both sides by 60 we get the ratio

1 mi. to

then mult. both sides by 75 we get the ratio

75 mi. to

simplifying we get

75 mi. to

or 1.25 hr.