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? Answers
A) 25 days
B) 88 days
C) 21 days
D) 11 days
E) 13 days

Rationale: "wc = 2 : 1 2 x + x = 1 / 7 x = 1 / 21 = > 21 days answer : c"
Answer: C