Urgently From pier against the current of the river the motor boat which own speed of 12 km/h went. In 40 min. after a boat exit it damaged the motor, and the boat a watercourse in 2 h was brought back to pier. What speed of a watercourse?

8

Resheniye:

let x is a watercourse, then (12th) is a speed with which the boat moved to the place of breakage, (12th) *4/6 - the distance passed by the boat to the place of breakage (40 min. =4/6ch =2/3ch), (2*kh) - the distance passed by the boat from the place of breakage to pier. we work out the equation: (12th) *2/3=2kh 8-2x/3=2x

to

2x/3=2x-8

to

2x/3-2x=-8

to

-4x/3=-8

to

of x=-8/-4/3

to

of x=6 of km/h

the Speed of a watercourse is equal to 2.4 km/h
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