A motor boat can travel 30km upstream and 28km downstream in 7 hours. It can travel 21km up stream and return in 5hrs.FInd the speed of the boat in still water and speed of the stream
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Upstream speed =30/7
Down speed =28/7
Add both =58/7
Now it covers up and down =21+21=42km in 5hrs
So up and down speed in still =42/5
Now difference =58/7-42/5=(58×5-42×7)/7×5
=(290-295)/35=-5/35
Stream speed =5/35kmph
Speed of the boat in still stream =30/7-5/35=145/35=4.14kmph
Down speed =28/7
Add both =58/7
Now it covers up and down =21+21=42km in 5hrs
So up and down speed in still =42/5
Now difference =58/7-42/5=(58×5-42×7)/7×5
=(290-295)/35=-5/35
Stream speed =5/35kmph
Speed of the boat in still stream =30/7-5/35=145/35=4.14kmph
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