Correct option is B
Given:
Rivers A and B merge at point P to form river C.
Water speeds:
River A = a
River B = b
River C = c
A boat travels from Q to R (against the current of river C, and then against river B’s flow).
Boat speed in still water = s
Solution:
When a boat goes upstream, the effective speed of the boat is s − water speed.
If the boat wants to move against the current, its speed s must be greater than the speed of the river current.
Here:
From Q to P → the boat moves upstream in river C, so it must have s > c
From P to R → the boat moves upstream in river B, so it must have s > b
Therefore:
The boat must have speed greater than both b and c, i.e.,
s must be greater than max(b, c)
Final Answer:
S. Ans. = maximum of b and c
