Question 1193094
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Mr. Downey can build a wall in 9 hours. His son Carl can build the same wall in 18 hours. 
Mr. Downey started to build the wall, worked for 3 hours, and then stopped working. 
How many hours would Carl require to complete the wall?
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Working for 3 hours, Mr. Downey completed 1/3 of the job; 2/3 of the job remained.


Hence, his son Carl needs 2/3 of 18 hours to complete the remaining job.


<U>ANSWER</U>.  Carl needs 12 hours to complete the job.
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Solved.