Correct Answer - Option 1 : 14 km
Given:
When speed is 15 kmph reaches 9 min late
When speed is 40% more reaches 7 min early
Formula:
Speed = distance/time
Calculation:
Let the distance be 'x' km
Therefore time taken to cover 'x' km at 15 kmph = x/15 hr
New speed = 15 + (40/100) × 15 = 15 + 6 = 21 kmph
Time taken to cover 'x 'km at 21 kmph = x/21 hr
But it is given that the difference between two timings
⇒ 9 + 7 = 16 min = 16/60 hr
⇒ x/15 – x/21 = 16/60
⇒ (21x − 15x)/(15 × 21) = 4/15
⇒ 6x/(15 × 21) = 4/15
⇒ x = 14 km
∴ Distance from home to coaching class is 14 km