Final answer:
To find the fraction of the job completed by Bob and Jeff in 4 days, we need to know their individual rates. Assuming Bob completes 1/6 of the job in 1 day, the fraction completed by both Bob and Jeff in 4 days is 1/3. Jeff takes 12 days to complete the entire job alone.
Step-by-step explanation:
To find the fraction of the job completed by Bob and Jeff in 4 days, we need to know the rate at which they both work together. Let's assume that Bob completes 1/6 of the job in 1 day and Jeff completes 1/x of the job in 1 day. Since they work together for 4 days, the fraction of the job completed by Bob and Jeff is:
(4 * (1/6)) + (4 * (1/x)) = 4/6 + 4/x = 2/3 + 4/x
To determine the value of x, we can use the information given in the options. The correct option is d, which states that Jeff takes 12 days to finish the entire job alone. Therefore, x = 12. Substituting the value of x into the equation, we can find the fraction of the job completed by Bob and Jeff in 4 days:
(2/3) + (4/12) = 2/3 + 1/3 = 3/3 = 1
Therefore, the fraction of the job completed by Bob and Jeff in 4 days is 1, which means the entire job is completed.
The correct option is d. 1/3.