Correct Answer - Option 3 : 1 1/2 hr
Given:
Speed = 45% = 9/20
Time = 1 hour 50 min = 11/6
Formula used:
Speed = Distance/Time
Speed is inversely proportional to time
Calculation:
Let the speed of the man be 20x
45% of the speed = 20x × 9/20
⇒ 9x
Ratio of speed of man before and after = 20x : 9x
As we know that, speed is inversely proportional to time
Time ratio of man before and after = 9x : 20x
According to the question
⇒ 20x/9 – x = 1 hr 50 min = (1 + 50/60) hr
⇒ 11x/9 = 11/6
⇒ 11x = 11 × 9/6
⇒ 11x = 33/2
⇒ x = 3/2 hr
⇒ 1 1/2 hr
∴ The usual time to reach the destination is 1 1/2 hr