Question 25632
A worker can cover a parking lot with asphalt in ten hours.
HENCE IN 1 HOUR HE CAN DO 1/10 JOB.
 With the help of an assistant, they can do the job in six hours.
HENCE IN ONE HOUR BOTH (HE+ASSISTANT)CAN DO 1/6 JOB
 How long would it take the assistant, working alone, to cover the parking lot with asphalt
HENCE IN 1 HOUR ASSISTANT ALONE CAN DO 1/6 - 1/10 JOB =(5-3)/30=2/30=1/15 JOB
HENCE ASSISTANT ALONE CAN DO 1 JOB IN 1/(1/15) HOURS = 15 HOURS.