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?
Pick:
A) 3 days B) 4 days C) 5 days D) 6 days E) 7 days
Explanation:   1/7 + 1/14 + 1/28 = 7/28 = 1/4 =&gt; 4 days   Answer: 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?