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) 11 days	B) 13 days	C) 21 days	D) 16 days	E) 18 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.