A boat goes 2km upstream and 3km down stream in 20min it goes 7km upstream and 2km down stream in 53min.what is the speed of the boat in still water?
Answers
speed of the boat in still water = 19.3 km/hr (135/7 km/hr)
Step-by-step explanation:
Let say Boat Speed in Still Water = B km/hr
Stream Speed = S km/Hr
Speed up stream = B - S km/Hr
Speed Down stream = B + S km/hr
A boat goes 2km upstream and 3km down stream in 20min
=> 2/(B - S) + 3/(B + S) = 20/60
it goes 7km upstream and 2km down stream in 53min
=> 7/(B - S) + 2/(B + S) = 53/60
Let say 1/(B-S) = X & 1/(B + S) = Y
2x + 3y = 20/60 Eq1
7x + 2y = 53/60 Eq1
3*Eq2 - 2 * Eq1
=> 17x = 119/60
=> x = 7/60
y = 2/60 = 1/30
B - S = 60/7
B + S = 30
=> 2B = 60/7 + 30
=> 2B = 270/7
=> B = 135/7 km/hr
= 19.3 km/hr
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