A, B and C can do a piece of work in 7 days, 14 days and 28 days respectively. How long will they taken, if all the three work together?
Choose the correct option.
A) 3 days
B) 4 days
C) 5 days
D) 6 days
E) None of these
Explanation:   1/7 + 1/14 + 1/28 = 7/28 = 1/4 =&gt; 4 days   ANSWER IS 4 days
<result>B</result>
A, B and C can do a piece of work in 7 days, 14 days and 28 days respectively. How long will they taken, if all the three work together?