9514 1404 393
Answer:
increasing 7/24 ft per week
Step-by-step explanation:
An expression for the length of the base can be written from the Pythagorean theorem relation between the sides of the triangle.
If the height is 7-x, where x is the number of weeks after the height is 7 feet, then the base length is ...
b = √(25^2 -(7-x)^2) = √(625 -(49 -14x +x^2)) = √(-x^2 +14x +576)
Then the rate of change of b with respect to x is ...
b' = (-2x +14)/(2√(-x^2 +14x +576))
When x=0, the rate of change of the base is ...
b' = 14/(2√576) = 7/24
The base is increasing 7/24 ft per week when the height is 7 ft.
Answer:
- plane: 550 mph
- wind: 50 mph
Step-by-step explanation:
If p and w represent the speeds of the plane and wind, respectively, the speed into the wind is ...
p - w = (3000 mi)/(6 h) = 500 mi/h
And, the speed with the wind is ...
p + w = (3000 mi)/(5 h) = 600 mi/h
Adding these two equations gives us ...
2p = 1100 mi/h
p = 550 mi/h . . . . . . . divide by 2
Then the wind speed is ...
w = 600 mi/h - p = (600 -550) mi/h
w = 50 mi/h
The rate of the plane in still air is 550 mi/h; the rate of the wind is 50 mi/h.
