alphabeta1234 wrote:
I am stumped by this question.
Al's rate is 1 Job / 8 Hours
Boris's rate is 1 Job/ 5 Hours
Cody's rate is 2 Job /8 Hours
When the question states that the second job required "twice the amount of work as the first" how does one interpret this? In the above posts you have the the time doubled, ie, Al's rate is no longer 1/8 but 1/16 (so the time to complete the job was doubled). But I saw it more as his rate to complete the job stayed the same and the job grew by a multiple of 2, ie, (1/8)*time_Al=2 job
The rate should be doubled in the numerator and the denominator.So Al's rate of 1 Job/8 Hour becomes (2*1 Job/2*8 Hour)=2 Job/16 Hour
Very confused.
Al can complete a particular job in 8 hours. Boris can complete the same job in 5 hours. Cody can complete a second job, which requires twice as much work as the first, in 8 hours. If all three people work together on the larger job for 2 hours, how long, in hours, would it take Al, working alone, to finish the job?A. 0.8
B. 3.0
C. 6.8
D. 8.0
E. 8.8
Al can complete a particular job in 8 hours, hence he can complete the second job which
requires twice as much work as the first in 16 hours --> the rate of Al for this larger job is 1/16 job/hour;
Boris can complete a particular job in 5 hours, hence he can complete the second job which requires twice as much work as the first in 10 hours --> the rate of Boris for this larger job is 1/10 job/hour;
The rate of Cody for this larger job is 1/8 job/hour.
In 2 hours all three would complete 2*(1/16+1/10+1/8)=23/40 part of the larger job, so 17/40 part of it is left to be done.
Al can complete it in time=job/rate=(17/40)/(1/16)=34/5=6.8 hours.
Answer: C.
Hope it's clear.
. it is assumed that Al and Boris too takes twice the amount of time and that double time is not applicable solely to Cody.