The speed of current is 6 mph. If there is no current, then boat would go with speed of 10 mph
Solution:
Formula to remember for this problem:
If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then:
Speed downstream = (u + v) km/hr
Speed upstream = (u - v) km/hr
Given that Traveling downstream a certain boat went 16 mph
let s = the boat speed in still water
let c = the rate of the current
s + c = 16 --- eqn 1
Also given that Traveling upstream it only went 4 mph
s - c = 4 ----- eqn 2
Add eqn 1 and eqn 2
s + c = 16
s - c = 4
(+) ----------------
2s = 20
s = 10
Substitute s = 10 in eqn 1
10 + c = 16
c = 6
Thus the speed of current is 6 mph
How fast would the boat go if there were no current?
We have found out that speed of current is 6 mph
If there is no current means,
s - c = 4
s - 6 = 4
s = 10 mph
Thus if there is no current, then boat would go with speed of 10 mph