John, Mac and Tonny together can do a work in 20 days. John alone can do the work in 80 days and Mac alone can do the same work in 70 days. Find in what time Tonny alone can do that work? Choose the most appropriate option.
A) 50days  B) 43.08days  C) 53.80days  D) 35days  E) 44.50days
The required answer is = 20*80*70 / 80*70-20(80+70)   = 112000/2600 = 43.08days   Answer is 43.08days
<result>B</result>
John, Mac and Tonny together can do a work in 20 days. John alone can do the work in 80 days and Mac alone can do the same work in 70 days. Find in what time Tonny alone can do that work?