This is an independent topic guide, not the official syllabus. Compare it with the current paper outline and rules published by the examination authority.
01 / UNDERSTANDING
Learning objectives
Cover still-water speed, upstream and downstream speed, equation recovery and trip time. The objective is to explain the current’s directional contribution before using half-sum or half-difference shortcuts.
02 / UNDERSTANDING
The concept in context
In a simplified constant-current model, downstream speed equals still-water boat speed plus stream speed, while upstream speed equals boat speed minus stream speed. Speeds must share units and upstream progress requires the boat’s still-water speed to exceed the current. Time still follows distance divided by the relevant ground speed.
03 / UNDERSTANDING
A worked learning case
Original educational case. An original boat moves at 10 km/h in still water while the stream is 2 km/h. It travels downstream at 12 km/h and upstream at 8 km/h. A 24-km trip takes two hours downstream but three hours upstream. The same distance has different travel times because the stream changes speed relative to the riverbank.
ORIGINAL EDUCATIONAL PRACTICE
Try it before you check.
Original practice: Downstream speed is 15 km/h and upstream speed is 9 km/h. What is the stream speed under the stated model?
Show the answer and reasoning
3 km/h.
Subtract the upstream equation from the downstream equation: the still-water speed cancels, leaving twice the stream speed. The difference is 15 − 9 = 6 km/h, so the stream speed is 3 km/h. The still-water speed is 12 km/h, and substituting confirms 12 + 3 = 15 and 12 − 3 = 9.
Two traps to watch for.
- Using the full downstream-upstream difference as stream speed.
- Applying the downstream speed to an upstream travel time.
YOUR TOPIC-SPECIFIC LEARNING MAP
Your revision map
Label boat speed and stream speed.
Write both ground-speed equations.
Substitute recovered values as a check.
Explain the idea, apply it to a new situation, then check what changed in your reasoning.
BANKERS TUTORIAL · SOURCE NOTES
Keep the source alongside your notes.
Official links provide subject context and authoritative reference material. This guide’s explanation, scenario and question are original Bankers Tutorial learning content.
- www.ibps.in https://www.ibps.in/
- www.ibps.in https://www.ibps.in/index.php/faq/
For IBPS & RRB preparation, check the current official notice before relying on changing dates, rules or examination requirements.
