Answer:
Current speed is 40mph
Step-by-step explanation:
We firstly need to know what is intended by upstream and downstream. When the boat travels in the direction of the current (horizontal movement of the water), we say it is moving downstream otherwise it is moving upstream.
Let's assume the speed of the boat is A and that of the current is B, then the speed when it moves dowstream would be A + B and the speed if it moves upstream would be A – B.
In this question, we know that the speed of the boat is 40mph. Given that it takes the same time to travel 8miles upstream as it does to travel 24miles downstream, we have
Speed upstream = 8/t
Speed downstream = 24/t
Respectively.
Let speed of current be X, then
Speed downstream = 40 + X
Speed upstream = 40 – X
From the question we have:
(40 + x)/24 = (40 – X)/8
(40 + x)/3 = (40 – x)/1
3(40 – x) = 40 + X
120 – 3x = 40 – X
120 – 40 = 3x – X
2x = 80
X = 40.
Therefore, current speed is 40mph
