Official Solution: At a distribution center, stations A and B scan packages at their respective constant rates. How many more hours does it take station B, working alone, to scan a new shipment of packages than it takes station A, working alone? Let \(a\) be the number of hours station A takes to scan the shipment alone, and let \(b\) be the number of hours station B takes to scan the shipment alone. The question asks for \(b - a\).
(1) The ratio of the time it takes station B, working alone, to scan the shipment to the time it takes station A, working alone, to scan the shipment is \(4:1\).
So:
\(b = 4a\)
This gives only the relationship between the two times, not the actual number of hours.
Not sufficient.
(2) The ratio of the time it takes stations A and B, working together, to scan the shipment to the time it takes station A, working alone, to scan the shipment is \(4:5\).
Station A’s rate is \(\frac{1}{a}\), and station B’s rate is \(\frac{1}{b}\). Thus, their combined rate is:
\(\frac{1}{a} + \frac{1}{b} = \frac{a + b}{ab}\)
So the time they take together is:
\(\frac{ab}{a + b}\)
Statement (2) tells us that the ratio of the together time to station A’s alone time is \(4:5\):
\(\frac{\frac{ab}{a + b}}{a} = \frac{4}{5}\)
\(\frac{b}{a + b} = \frac{4}{5}\)
\(5b = 4a + 4b\)
\(b = 4a\)
This gives the same relationship as statement (1), but not the actual value of \(a\) or \(b\).
Not sufficient.
(1)+(2) Each statement gives the same relationship:
\(b = 4a\)
Thus, even after combining the statements, we still know only the relationship between the two times, not the actual value of either time. Therefore, \(b - a\) cannot be determined.
Not sufficient.
Answer: E