A current's speed is 7 mph. A boat travels three times slower against the current that with the current. What is the speed of the boat in still water?
Let's call the speed of the boat in still water "x" mph. Against the current, the boat would be traveling at a speed of "x - 7" mph, and with the current, the boat would be traveling at a speed of "x + 7" mph.
Given that the boat travels three times slower against the current than with the current, we can set up the equation:
x - 7 = (x + 7) / 3
Multiplying both sides of the equation by 3 to eliminate the fraction, we get:
3(x - 7) = x + 7
Expanding the left side of the equation:
3x - 21 = x + 7
Subtracting "x" from both sides:
2x - 21 = 7
Adding 21 to both sides:
2x = 28
Dividing both sides by 2:
x = 14
Therefore, the speed of the boat in still water is 14 mph.
Let's assume the speed of the boat in still water is x mph.
Against the current, the boat travels at a speed of (x - 7) mph, as it is three times slower.
With the current, the boat travels at a speed of (x + 7) mph.
According to the given information, the boat's speed against the current is three times slower than with the current, so we can write the equation:
(x - 7) = 3(x + 7)
Now, let's solve the equation:
x - 7 = 3x + 21 [Distribute 3 to (x + 7)]
Subtract x from both sides:
-7 = 2x + 21
Subtract 21 from both sides:
-28 = 2x
Divide both sides by 2:
-14 = x
Therefore, the speed of the boat in still water is -14 mph. However, since speed cannot be negative, we can conclude that there is no possible solution for this problem.