ggatt said:
Tanya rowed a boat 1km upstream in one hour. Rowing at the same rate, she made the return trip downstream in 15 min. Find the rate of the current.
- i need to figure out the equation and i started it but im not sure if it's right.. i did with current...1/4(r+c)....and then against current (r-c)
- please help!..thanks!
You should start any of these problems by defining the variables:
let r = rate in still water
let c = rate of the current
Going upstream, the speed of the boat in still water will be
decreased by the speed of the current, so the actual speed of the boat will be r - c. The distance traveled by the boat at this speed in 1 hour will be 1(r - c). We know that the distance traveled is 1 km (it says so in the problem). So,
1(r - c) = 1
or,
r - c = 1
Now, going downstream, the speed of the boat in still water will be
increased by the speed of the current, and the boat will travel at r + c km/hr. It takes 15 minutes, or 1/4 hour, for the boat to travel 1 km at this speed. So,
(1/4)(r + c) = 1
You can multiply both sides of this equation by 4 to eliminate the fraction:
r + c = 4
Ok...you've got two equations:
r - c = 1
r + c = 4
Can you take it from here?
