Thread: work problems

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.

Thanks for looking.

(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