the speed of a motorboat in still water to that of the current of water in the river are in the ratio 7:2. If the motorboat takes 3hrs 54mins to go to a certain distance in upstream, how long will it take to fo the same distance in downstream?
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Answer:
Step-by-step explanation:
Let x = speed of boat in still water
Let y = speed of the current
then
(x+y) = speed with the current
and
(x-y) = speed against the current
:
Write a distance equation for each trip: Dist = time * speed
;
2(x + y) = 50
3(x - y) = 45
;
Simplify divide the 1st equation by 2 and the 2nd equation by 3; results:x + y = 25
x - y = 15
------------addition eliminates y, find x
2x = 40
x = 40%2F2
x = 20 mph speed of boat in still water
:
Find y using; x + y = 25
20 + y = 25
y = 25 - 20
y = 5 mph speed of the river
:
:
Check solutions in the 2nd original equation
3(x - y) = 45
3(20-5) = 45
3(15) = 45;
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