A can have a piece of work done in 15 days, B can work three times faster than the A, C can work two times faster than A. How many days will they take to do the work together ? Choose the correct answer.
A) 3 days
B) 8/9 days
C) 10/3 days
D) can't say
E) none
A's 1 day work is 1/20   B's 1 day work is 3/20   10/3 days's 1 day work is 2/20   (A+B+10/3 days)'s 1 day work(1/20+3/20+2/20) is 3/10   so, they can finish the work in 10/3 days   ANSWER:10/3 days
<result>C</result>
A can have a piece of work done in 15 days, B can work three times faster than the A, C can work two times faster than A. How many days will they take to do the work together ?