A is twice as good a workman as B and they took 7 days together to do the work B alone can do it in. Choose the most appropriate option:
A) 71 days
B) 55 days
C) 21 days
D) 77 days
E) 44 days
W21 days = 2:1   2x + x = 1/7   x = 1/21 =&gt; 21 days   Answer: 21 days
<result>C</result>
A is twice as good a workman as B and they took 7 days together to do the work B alone can do it in.