Question
Download Solution PDFA boat running downstream covers a distance of 20 km in 2 hrs while it covers the same distance upstream in 5 hrs. Then speed of the boat in still water is ?
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFGiven:
Downstream distance: 20 km
Downstream time: 2 hrs
Upstream distance: 20 km
Upstream time: 5 hrs
Concept:
The speed of the boat in still water is the average of its speeds downstream and upstream.
Formula Used:
Speed downstream (Vd) = Distance / Time
Speed upstream (Vu) = Distance / Time
Speed of boat in still water (Vb) = (Vd + Vu) / 2
Calculation:
⇒ Speed downstream (Vd) = 20 km / 2 hrs
⇒ Vd = 10 km/hr
⇒ Speed upstream (Vu) = 20 km / 5 hrs
⇒ Vu = 4 km/hr
⇒ Speed of boat in still water (Vb) = (10 km/hr + 4 km/hr) / 2
⇒ Vb = 14 km/hr / 2
⇒ Vb = 7 km/hr
∴ The speed of the boat in still water is 7 km/hr.
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