Question 1181303
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Carlo worked for 2 hours alone and then 4 hours with Bobby, for a total of 6 hours.  Since he can do the whole job in 10 hours, the fraction of the job that he did is 6/10 = 3/5.<br>
So Bobby did 2/5 of the job.  He worked for 4 hours with Carlo and then 6 more hours alone, for a total of 10 hours.<br>
Since he did 2/5 of the job in 10 hours, the amount of time it would take him to do the job alone is {{{10/(2/5)=10*(5/2)=25}}}<br>
ANSWER: 25 hours<br>