A man’s rate with the current is 12 km/h; the current is 1.5 km/h. Find his rate against the current.

Introduction / Context:
With-current and against-current speeds differ by twice the stream speed around the still-water rate.

Given Data / Assumptions:

• b + s = 12 km/h; s = 1.5 km/h.

Concept / Approach:
Compute still-water b, then subtract s to get upstream.

Step-by-Step Solution:

Final Answer:
9 km/hr