Answer:
Speed of the bob when there is no current is 4 km/hr
Explanation:
Let the Bob swam v km/hr without the current '
Speed of current is 2 km/hr
So speed in the direct of current = v+2 km/hr
And speed against the direction of current = v-2 km/hr
It is given that Bob swam 4 km against the current in the same time as swam 12 km in direct of current , means time is same
We know that time [tex]=\frac{distance}{speed}[/tex]
So [tex]\frac{4}{v-2}=\frac{12}{v+2}[/tex]
[tex]4v+8=12v-24[/tex]
8 v = 32
v = 4 km/hr
So speed of the bob when there is no current is 4 km/hr