If a group of 5 skilled workers take 3 hours to finish a job, how long will it take a group of 4 apprentices to do the same job?
Since 5 skilled workers take 3 hours to finish the job then 1 skilled worker takes 3*5=15 hours to finish the job (so the rate of 1 skilled worker is 1/15 job/hour).
(1) An apprentice works at 2/3 the rate of a skilled worker --> one apprentice takes 3/2*15=45/2 hours to finish the job, hence 4 apprentices will take (45/2)/4=45/8 hours to finish the job. Sufficient.
(2) The 5 skilled workers and the 4 apprentices working together will take 1 22/23 hours to finish the job --> say the rate of one apprentice is x job/hour, then 1/3+4x=23/45. We can find x. Sufficient.
As in the question stem there is nowhere mention that, all 5 skilled workers work at the constant and equal rate, according to me, statement 1 is insufficient, as we have assumed that all are working at constant rates.
Statement 2 is sufficient,
Hence B for me.