How many kilometers the motor ship will pass in 6 hours moving against

How many kilometers the motor ship will pass in 6 hours moving against the river flow if its own speed is 21 km / h and the current speed is 2 thirty-fifths of the boat’s own speed.

1) Let’s calculate what the river flow rate is equal to: 21: 35 · 2 = 1.2 (km / h);

2) Let us subtract the speed of the river flow from the own speed of the motor ship and determine what the speed of the motor ship against the current is equal to: 21 – 1.2 = 19.8 (km / h);

3) Let’s find how many km the motor ship will pass against the current in 6 hours: 19.8 · 6 = 118.8 (km).

Answer: the ship will pass in 6 hours 118.8 km.