Correct Answer - Option 1 : 9 km
Given:
When speed is 30 kmph reaches on time
When speed is 18kmph reaches 12 min early
Formula:
Time = distance/speed
Calculation:
Let the distance be 'x' km
Therefore time taken to cover 'x' km at 30 kmph = x/30 hr
Time taken to cover 'x 'km at 18 kmph = x/18 hr
But it is given that the difference between two timings
⇒ 0 + 12 = 12 min = 12/60 hr = 1/5
⇒ x/18 – x/30 = 1/5
⇒ (30x − 18x)/(18 × 30) = 1/5
⇒ 12x/(18 × 30) = 1/5
⇒ x = (1 × 18 × 30)/(12 × 5)
⇒x = 9 km
∴ Length of journey is 9km.