An airplane travels a specific distance at a speed of 240 km/h over the course of 5 hours. To cover the same distance in just 1 hour, it needs to fly at a speed of:

Correct — A. The distance stays the same, so find it first.

Distance = speed × time = 240 × 5 = 1200 km
New time = 1 hour
Speed needed = distance ÷ time = 1200 ÷ 1 = 1200 km/h → option (a)

Why the others are wrong

• (b)
  1500 km/h — 1500 km/h covers 1500 km in an hour, 300 km more than the 1200 km route. The plane would land after 1200 ÷ 1500 = 0.8 hour, or 48 minutes.
• (c)
  1400 km/h — 1400 km/h overshoots the target: 1200 ÷ 1400 = 6⁄7 hour, about 51 minutes. The question asks for exactly 1 hour.
• (d)
  1600 km/h — 1600 km/h flies the 1200 km in 1200 ÷ 1600 = 3⁄4 hour, or 45 minutes, a quarter of an hour sooner than the 1 hour allowed.

Distance = speed × time. When the distance is fixed, speed × time stays constant, so speed and time change by the same factor in opposite directions.

Here the time falls from 5 hours to 1, a factor of 5, so the speed rises by that factor: 240 × 5 = 1200 km/h. Finding the distance and dividing by the new time gives the same number.

Key facts

• Distance = speed × time.
• For a fixed distance, S₁ × T₁ = S₂ × T₂.
• Here 240 × 5 = 1200 × 1 = 1200.

Common traps

• Answering with the increase, 1200 − 240 = 960 km/h, when the question asks for the new speed
• Multiplying the speed by the new time (240 × 1) instead of the original 5 hours to get the distance

No directly related past PYQ was found.