Paper 1 · Mathematical Reasoning and Aptitude
UGC NET December 2021 June 2022 (09.07.2022) Shift-I
An aeroplane started 30 minutes later than the scheduled time from a place 1500 km away from its destination. To reach on schedule, the pilot increased the speed by 250 km/hr. What was the speed of the aeroplane during the journey (in km/hr)?
A750
B1000 ✓ Correct
C800
D900
Correct answer: (B) 1000 — The speed during the journey was 1000 km per hour.
Explanation
★The speed during the journey was 1000 km per hour.
★Let the usual time be x hours for the 1500 km trip.
★Starting 30 minutes late, the plane must cover 1500 km in x minus half an hour.
★The extra speed of 250 comes from covering the same distance in less time.
★Setting 1500 over (x minus half) minus 1500 over x equal to 250 gives a quadratic in x.
★Solving the quadratic gives x equal to 2 hours.
★So the journey speed is 1500 divided by 1.5, which is 1000 km per hour.
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