Aptitude - Boats and Streams - Discussion

@All.

Against the current - upstream.
Along the current - downstream.

If they mentioned the question like "the speed of the man is...", definitely the answer will be 12.5 km/hr, ie. upstream = speed of the man - speed of the current = 15-2.5=12.5 km/hr.

But,
The question was like "Speed of the man with the current".

ie., 15km/hr is the summation of the speed of the man and the current. so we need to subtract the speed of the current from 15, to know man's speed in water.
ie., 15 - 2.5 = 12.5 => man's speed.
After the above step, we can easily find the man's speed against the current by using the formula below:
upstream = speed of the man - speed of the current.
= 12.5 - 2.5 = 10 km/hr.

Not yet understand the solution. Please help me to get this.