Question

A and b can do a job in 12 days,b and c in 15 days and c and a in 20 days. how long would a take to do that work?

Answer 1

1/a+1/b=1/12. 1/b+1/c÷1/15. 1/c+1/a=1/20 solution gives a=30. b =20. c=60. when all three work 1/30+1/20+1/60=1/10. Work completed in 10 days.