Q115
ArithmeticSpeed, Time & Distance
With an average speed of 40km/hr, a train reaches the destination on time. If it runs with average speed 35km/hr, it is late by 15mins. The length of the total journey is:
- a.30 km
- b.180 km
- c.40 km
- d.140 km
No option is correct as printed — this question is disputed. WBPSC awarded the mark to all candidates: no correct option — the journey works out to 70 km, which is not listed (140 km would need a 30-minute delay).
The extra time is $\frac{d}{35} - \frac{d}{40} = \frac{d}{280}$ hours, and setting this to $\frac{1}{4}$ hour gives d = 70 km. 70 km is not among the options; 140 km would make the train 30 minutes late. The Commission therefore awarded the mark to all candidates.