MATHS AROUND US ONLINE LESSON – 27th APRIL 2018
TASK ABOUT MOVEMENT Ivan and Peter train river rowing. They passed 12 km along the flow of the river for an hour and a half. When they began to row with the same force but against the flow of the river, they realized that their boat was stationary standing to the riverbank. They were too tired and in order to get home faster, they took a motorboat that speed was 28 km/h in calm water. How long did it take them to come back? Solution: Along the flow of the river: s v.t 12 v.1,5 12 120 v 8km / h (the speed of the boat along the flow of the river) 1,5 15
vл vт 0 vт vл vт vл 8 2.vт 8 vт 4km / h
Against the flow of the river: vмл 28 4 24km / h
Back – 12 km. They will be back in half-hour ( 30 minutes )