24- 18=6
∴ sailing downstream12km = sailing upstream for 6km.
It takes seven hours for a ship to sail 36 kilometers downstream and 24 kilometers downstream.
It takes seven hours for a ship to sail 84 kilometers downstream.
The speed of the ship sailing in the water is12km/h.
Similarly, the speed of sailing against the current is 6 km/h.
∴72/ 12+24/6= 10
It takes 10 hour to sail 72 kilometers downstream and 24 kilometers upstream.
Equation solution:
Let the downstream speed be x and the upstream speed be y.
Then 36/x+24/y=48/x+ 18/x=7.
∴x= 12 y=6
∴72/ 12+24/6= 10
It takes 10 hour to sail 72 kilometers downstream and 24 kilometers upstream.
(1) How many courses should North American actuaries take?
Actuaries in North America need to take seven courses.
1. Probability theory (probability)
Ex