(i)Alice does 1 per hour and her sister 2 per hour. Therefore they can do 3 per hour and 1 is going to take them 20 minutes.
(ii) It is going to show the correct time again when it has lost 12 hours. It is going to take
1. Alice needs 1 hour to do a certain job. Betty, her older sister, can do the same job in 1/2 hour. How many minutes will it take them to do the job if they work together at the given rates?
2. A twelve hour clock loses 1 minute every hour. Suppose it shows the correct time now. What is the least number of hours from now when it will again show the correct time.
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