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Answer:
<em>Roberto's speed in still water is 6 miles/hour and the river speed is 2 miles/hour</em>
Step-by-step explanation:
<u>Relative Speed</u>
When a body is moving at a constant speed v, the distance traveled in a time t is:
When Roberto rows downstream, his speed in still water is added to the speed of the water, making it easier to travel the required distance.
When Roberto rows upstream, his speed in still water is affected by the speed of the water, both are subtracted and the required distance is covered in more time.
Let's call
x = Roberto's rowing speed in still water
y = Speed of the river current
The speed when rowing downstream is x+y, thus the distance traveled is
Where t1=2.5 hours. Substituting values:
Rearranging, we find the downstream equation:
The speed when rowing upstream is x-y, and the distance traveled is
Where t2=5 hours. Substituting values:
Rearranging, we find the upstream equation:
Multiplying [1] by 2:
Adding this equation to [2]:
Solving:
Dividing [2] by 5:
Solving for y
Thus, Roberto's speed in still water is 6 miles/hour and the river speed is 2 miles/hour
Answer:
280 cubic inches
Step-by-step explanation:
Cubic inches of foam required = volume of the box - volume of the basketball
The box has a shape of a cube, so that;
volume of the box =
where l is the length of the sides of the box.
volume of the box =
= 729 cubic inches
volume of the box = 729 cubic inches
The basketball has the shape of a sphere, so that;
volume of the basketball =
= x 3.14 x
= 448.693
volume of the basketball = 448.693 cubic inches
Thus,
cubic inches of foam required = 729 - 448.693
= 280.307
The cubic inches of foam to be used is 280 cubic inches.