working together , a and b can do a job in 6 days . b and c can do the same job in 10 days , while c and a can do it in 7.5 days . how long will it take if all a , b and c work together to complete the job ?
a and b 1 day work = 1 / 6 b and c 1 day work = 1 / 10 c and a 1 day work = 1 / 7.5 a , b , c 1 day work = ( 1 / 6 + 1 / 10 + 1 / 7.5 ) * 1 / 2 = 1 / 5 so a . b . c completes work in 5 days answer : b
inverse(divide(add(add(inverse(6), inverse(10)), inverse(7.5)), const_2))