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.  Pick one:	A) 17 days	B) 21 days	C) 29 days	D) 25 days	E) 27 days
WC = 2:1   2x + x = 1/7   x = 1/21 =&gt; 21 days   ANSWER:21 days
<result>B</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.