Answer: the speed of the boat on the lake is 9 mph
Step-by-step explanation:
Let x represent the speed of the boat on the lake or in still water.
The speed of the current in a river is 6 mph. This means that if the boat goes upstream against the speed of the current, its total speed would be (x - 6)mph. If the boat goes downstream against the speed of the current, its total speed would be (x + 6)mph.
Time = distance/ speed
Every day, his route takes him 22.5 miles each way against the current and back to his dock, and he needs to make this trip in a total of 9 hours. This means that the time taken to travel upstream is
22.5/(x - 6). The time taken to travel downstream is
22.5/(x + 6)
Since the total time is 9 hours, it means that
22.5/(x - 6) = 22.5/(x + 6)
Cross multiplying, it becomes
22.5(x + 6) + 22.5(x - 6) = 9
Multiplying through by (x + 6)(x - 6), it becomes
22.5(x - 6) + 22.5(x + 6) = 9[(x + 6)(x - 6)]
22.5x - 135 + 22.5x + 135 = 9(x² - 6x + 6x - 36)
22.5x + 22.5x = 9x² - 324
9x² - 45x - 324 = 0
Dividing through by 9, it becomes
x² - 5x - 36 = 0
x² + 4x - 9x - 36 = 0
x(x + 4) - 9(x + 4) = 0
x - 9 = 0 or x + 4 = 0
x = 9 or x = - 4
Since the speed cannot be negative, then x = 9
Need to see more instructions.
Answer:
y=29*x
Step-by-step explanation:
This problem is a linear function problem. We need at least two points to solve it. After finding two points we will compute the slope and then us the point-slope formula.
If you put 11 gallons of gasoline in your car it will allow you to drive 319 miles, this means that when x= 11 then, y=319. So the first point is (11,319). For the second point you now that if you have no gallons of gasoline then you won't be able to drive so, the second point is (0,0).
Now that we have to points we are able to compute the slope. The formula for the slope is:
.
this way
.
.
Now that we have the slope, we can use the point-slope formula to get the equation. The point-slope formula is:
(here it doesn't matter which point you use, you will get the same result).
Substituting the point (11,319) and the slope:
And we finaly get the equation!
Answer: 12/25
Explanation:
48/100 = 24/50 = 12/25
