Solution:
GIven:
Ravi starts from his house to school at 8:20 a.m with speed of 10 km/h and reaches 8 minutess late
If he ride the cycle at speed of 16 km/h he reaches his school 10 minutes early
Formula used:
Calculation:
Let the distance between home and school be x km
And time take to reach school at the time be t hrs
With the speed of 10 km/h, Ravi reaches 8 minutes late
⇒ x/10 = t + 8/60
⇒ x/10 = t + 2/15 ----(1)
With the speed of 16 km/h, Ravi reaches 10 minutes early
⇒ x/16 = t – 10/60
⇒ x/16 = t – 1/6 ----(2)
Now, Subtract (2) from (1)
⇒ x/10 – x/16 = t + 2/15 – t + 1/6
⇒ (5x – 8x)/80 = (4 + 5)/30
⇒ 3x × 30 = 9 × 80
⇒ x = 720/90
⇒ x = 8 km
Now, put the value of x in (1)
⇒ 8/10 = t + 2/15
⇒ t = 8/10 – 2/15
⇒ t = (24 – 4)/30
⇒ t = 2/3
To convert it into minutes by 60
⇒ (2/3) × 60 = 40 minutes
College starts at 8:20 + 40 mins = 9 A.M
∴ College starts at 9 A.M
Short Cut::
⇒ 8x = 48 minutes
Ravi is 8 min late, the correct time will be
⇒ 48 - 8 = 40 minutes
College starts at 8:20 + 40 mins = 9 A.M
∴ College starts at 9 A.M
