Question 1134009
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Obviously one of the answers you have received makes no sense; it can't take them 2 hours and 4 hours individually if it takes them 6 hours together.<br>
Here is a different way than shown by the other tutor to get the correct answer of 9 hours for the time it takes Andrea to do the job alone.<br>
(1) It takes Andrea half as long as Samantha to do the job; that means she works twice as fast as Samantha.<br>
(2) When working together, the two of them take 6 hours to do the job; and, since Andrea works twice as fast as Samantha, she does 2/3 of the job.<br>
(3) Then since Samantha does 2/3 of the job in 6 hours, she can do the whole job herself in (3/2) times 6 hours, or 9 hours.