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 correct option.
A) 23 days B) 25 days C) 21 days D) 26 days E) 29 days
21 days   21 days   W21 days = 2:1   2x + x = 1/7   x = 1/21 =&gt; 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.