Question 1191073
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Another mental solution that gives you good mental exercise....<br>
Since Fred takes 1/3 as long as John to do the job, when they work together Fred does 3/4 of the work while John does 1/4.<br>
Since it take them 1 1/2 hours to do the job together, that means Fred does 3/4 of the job in 1 1/2 hours; and that means it would take him 4/3 times 1 1/2 hours, or 2 hours, to do the job alone.<br>
ANSWER: 2 hours<br>