79,39,19,9,4, ?
79-(1÷2)39-(1÷2)19-(1÷2)9-(1÷2)4-(1÷2)1.5
The respective ratio between the speed of the boat upstream and speed of the boat downstream is 2:3. What is the speed of the boat in still water if it covers 42 km downstream in 2 hours 20 minutes ? (in km/h)
17,9,10,16.5,35
71,78,92,120,?,288
1.5,2.5,7,24,100
264,262,271,243,308