Printing presses, Press A and Press B, are used to print the daily edition of a certain newspaper. Working together...

Understanding the Question

We need to find the exact number of hours it took for Press A and Press B working together to print yesterday's daily edition.

To answer this question with a specific time value, we need to know:

• The combined printing rate of both presses (newspapers per hour)
• The total number of newspapers in the daily edition

Think of it like asking how long a trip takes - we need both the speed AND the distance. Here, we need both the printing rate AND the quantity to print.

Analyzing Statement 1

Statement 1 tells us: Press A printed at \(4,000\) newspapers per hour yesterday.

This gives us Press A's rate, but we're still missing critical information:

• Press B's printing rate
• The total number of newspapers in the daily edition

Without knowing how fast Press B works or how many newspapers need to be printed, we cannot determine the time. It's like knowing one car travels at 60 mph but not knowing the companion car's speed or the trip distance.

Statement 1 is NOT sufficient.

This eliminates choices A and D.

Analyzing Statement 2

Now let's forget Statement 1 completely and analyze Statement 2 independently.

Statement 2 tells us: Press B printed at 75% of Press A's rate yesterday.

This gives us a relationship between the two rates (\(\mathrm{B} = 0.75 \times \mathrm{A}\)), but notice what's missing:

• We don't know Press A's actual rate
• We don't know Press B's actual rate
• We still don't know the total number of newspapers

Without concrete numbers for either rate or the job size, we cannot calculate time. We have a ratio but no actual values.

Statement 2 is NOT sufficient.

This eliminates choice B.

Combining Statements

Now let's use both statements together:

• From Statement 1: Press A's rate = \(4,000\) newspapers/hour
• From Statement 2: Press B's rate = 75% of Press A = \(0.75 \times 4,000 = 3,000\) newspapers/hour
• Combined rate = \(4,000 + 3,000 = 7,000\) newspapers/hour

Here's the crucial insight: We now know exactly how fast they work together (\(7,000\) newspapers per hour), but we still don't know HOW MANY newspapers are in the daily edition!

Without knowing the size of the daily edition, we cannot determine the time. For example:

• If the daily edition is \(70,000\) newspapers: Time = \(70,000 \div 7,000 = 10\) hours
• If the daily edition is \(140,000\) newspapers: Time = \(140,000 \div 7,000 = 20\) hours

The missing piece isn't about rates - it's about quantity.

The statements together are NOT sufficient.

This eliminates choice C.

The Answer: E

Despite knowing both printing rates, we cannot determine the time because we don't know the size of the daily edition. The question asks for a specific number of hours, which requires knowing both the rate AND the amount of work.

Answer Choice E: "The statements together are not sufficient."