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)?

The speed during the journey was 1000 km/hr.

Let scheduled speed = s; a 0.5 hr delay is offset by speed s + 250.

1500/s - 1500/(s + 250) = 0.5.

1500 * 250 = 0.5 * s(s + 250), so s(s + 250) = 750000.

s = 750, so journey speed = 750 + 250 = 1000 km/hr.