A, B and C can do a work in 90, 30 and 45 days respectively. If they work together, in how many days will they complete the work? Select the correct option:
A) 12 B) 10 C) 15 D) 8 E) 13
Option 15   Explanation:   One days's work of A, B and 15 = 1/90 + 1/30 + 1/45   = (1 + 3 + 2)/90 = 1/15   A, B and 15 together can do the work in 15 days.
<result>C</result>
A, B and C can do a work in 90, 30 and 45 days respectively. If they work together, in how many days will they complete the work?