Question

Susan, ella, and dolly can together complete a task in 10 days; ella, dolly, and kate can together complete it in 15 days; and ella and dolly take 30 days to complete the same task. Determine the number of days that all the 4 girls will take to complete the task while working together.

Answer 1

Answer:

7.5 days

Step-by-step explanation:

S and E and D can do a piece of work in 10 days: S+ E + D = 1/10-------(1)

E,D and  K can do the same work in 15 days: E + D+K = 1/15 -------(2)

E and D can do the same work in 30 days: E + D = 1/30 -------(3)

hence K can do the work in (2) -(3)= 1/15-1/30=1/30 , which means 30 days  

hence all four girls together will finish the work in 1/10+1/30= 4/30= 1/7.5

which means 7.5 days