A car traveled first 36 km at 6 km/h faster than the usual speed, but it returned the same distance at 6 km/h slower than usual speed. I the total time taken by car is 8 hours, for how many hours does it traveled at the faster speed ?

Answer: Option C

Let the original speed be S then,
Total time taken,
$$\frac{36}{\text{S}-6}+\frac{36}{\text{S}+6}$$    = 8 hours
On solving the equation, we get
S = 12, -3
Then possible value of S = 12 km/h.
Thus, time taken by car at faster speed = $$\frac{36}{12+6}$$  = 2 hours