Henrikh lives x blocks from his office. It takes him 1 minute per block to walk to
work and 20 seconds per block to ride his bicycle to work. If it takes him exactly
8 minutes more to walk to work than to ride his bicycle, then x equals Choose the correct choice from the following choices:
A) 4  B) 7  C) 12  D) 15  E) 20

Rationale: the best way would be . . . per km , he takes 40 secs extra if he walks so he will take 8 mins or 8 * 60 secs in 8 * 60 / 40 = 12 km answer : c
Answer: C