Answer:
4.3 hours
Step-by-step explanation:
Let the number of hours Sally does a job = x
Let the number did hours Joan does a job be equal to y
Sally and Joan were able to dust the house in 3 hours together.
1/x + 1/y = 1/3
It takes Joan 10 hours to finish the same job alone.
Hence,
1/x + 1/10 = 1/3
1/x = 1/3 - 1/10
Least common dey = 30
1/x = 10 - 3/30
1/x = 7/30
Cross Multiply
x × 7 = 30
7x = 30
x = 30/7
x = 4.2857142857 hours
Approximately = 4.3 hours
Without help, it would take Sally 4.3 hours to finish the same job.
