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
10 minutes more to walk to work than to ride his bicycle, then x equals	Options:
A) 4
B) 7
C) 10
D) 15
E) 20
The best way would be...   Per km, he takes 40 secs extra if he walks   So he will take 10 mins or 10*60 secs in 10*60/40= 
<gadget id="calculator">10*60/40</gadget>
<output>15</output>
15 km   ANSWER:15
<result>D</result>
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
10 minutes more to walk to work than to ride his bicycle, then x equals