Question Number 10069 by Tawakalitu ayo mi last updated on 23/Jan/17

A man can row a boat at 4 km/hr in still water.  He row the boat 2km upstream and 2km back  to his starting place in 2 hours. How fast is   the stream flowing.

Commented byridwan balatif last updated on 23/Jan/17

Commented byTawakalitu ayo mi last updated on 23/Jan/17

God bless you sir.

Answered by sandy_suhendra last updated on 23/Jan/17

let the velocity of the stream=x km/h  so the velocity upstream =(4+x) km/h  the velocity when he rows back=(4−x) km/h  the equation ⇒ (2/(4+x)) + (2/(4−x)) = 2                          ((2(4−x)+2(4+x))/((4+x)(4−x))) = 2                          ((8−2x+8+2x)/(16−x^2 )) = 2                                16−x^2 =8                                  x^2  = 8 ⇒ x=2(√2) km/h

Commented byTawakalitu ayo mi last updated on 23/Jan/17

God bless you sir.