An aeroplane covers a certain distance at a speed of 240 kmph in 5 hours. To cover the same distance in 123 hours, it must travel at a speed of:
Choose one
A) 234
B) 377
C) 720
D) 378
E) 268

Rationale: speed and time are inversely proportional ⇒ speed ∝ 1 time ( when distance is constant ) here distance is constant and speed and time are inversely proportionalspeed ∝ 1 time ⇒ speed 1 speed 2 = time 2 time 1 ⇒ 240 speed 2 = ( 123 ) 5 ⇒ 240 speed 2 = ( 53 ) 5 ⇒ 240 speed 2 = 13 ⇒ speed 2 = 240 × 3 = 720 km / hr answer : d
Answer: D