Railways Notes / Mathematics (Quantitative Aptitude) / Chapter 15
Chapter 15 of 31

Boats and Streams

Upstream-downstream speed relations, built directly on Relative Speed from the previous chapter.

📖 ~4 min read 📐 RRB NTPC / Group D — Mathematics

Core Formulas

TermFormula
Downstream speedBoat speed (b) + Stream speed (s)
Upstream speedBoat speed (b) − Stream speed (s)
Boat's speed in still water½ × (Downstream + Upstream)
Stream speed½ × (Downstream − Upstream)
💡 Example: Downstream speed=20 km/hr, Upstream=8 km/hr. Boat speed=½(20+8)=14 km/hr. Stream speed=½(20−8)=6 km/hr.
💡 Once you compute the effective (downstream/upstream) speed, apply plain Time = Distance/Speed as in the previous chapter.

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