Many mechanical calculators were powered by a notched cylinder mechanism called the Leibniz wheel. Leibniz wheel calculators were popular in...
GMAT Standard English Conventions : (Grammar) Questions
Many mechanical calculators were powered by a notched cylinder mechanism called the Leibniz wheel. Leibniz wheel calculators were popular in the first half of the twentieth ______ these ingenious devices were eventually replaced by electronic calculators.
Which choice completes the text so that it conforms to the conventions of Standard English?
century
century,
century, but
century that
Let's begin by understanding the meaning of this sentence. We'll use our understanding of pause points and segment the sentence as shown - understanding and assimilating the meaning of each segment bit by bit!
Sentence Structure
- Many mechanical calculators
- were powered
- by a notched cylinder mechanism
- called the Leibniz wheel.
- by a notched cylinder mechanism
- were powered
- Leibniz wheel calculators
- were popular
- in the first half of the twentieth century [?]
- were popular
- these ingenious devices
- were eventually replaced
- by electronic calculators.
- were eventually replaced
Understanding the Meaning
The first sentence gives us some background:
- "Many mechanical calculators were powered by a notched cylinder mechanism called the Leibniz wheel."
- This tells us about a specific mechanism (the Leibniz wheel) that was used to power mechanical calculators.
Now the second sentence starts:
- "Leibniz wheel calculators were popular in the first half of the twentieth century"
- So these calculators using this mechanism were popular in the early 1900s.
This is where we have the blank. Let's look at the choices:
- Choice A gives us nothing after "century"
- Choice B gives us a comma
- Choice C gives us a comma plus "but"
- Choice D gives us "that"
To see what works here, let's read the rest of the sentence and understand what it's saying!
- "these ingenious devices were eventually replaced by electronic calculators"
- So despite being these clever mechanical devices, they eventually got replaced by electronic calculators.
Now let's think about what we have here:
The part before the blank:
- "Leibniz wheel calculators were popular in the first half of the twentieth century"
- This is a complete thought - it has a subject (calculators), a verb (were), and expresses a complete idea
- It could stand alone as its own sentence
The part after the blank:
- "these ingenious devices were eventually replaced by electronic calculators"
- This is also a complete thought - it has a subject (devices), a verb (were replaced), and expresses a complete idea
- This could also stand alone as its own sentence
What do we notice about the relationship between these two parts?
- The first part says the calculators were popular (a positive statement about their success)
- The second part says they were replaced (showing they didn't last)
- There's a contrast here - even though they were popular, they still got replaced
When you have two complete thoughts that you want to join together in one sentence, you need proper punctuation to connect them. And when those thoughts contrast with each other, we need a word that shows that contrast.
So we need: a comma + "but" (the word "but" signals the contrast between being popular and being replaced)
The correct answer is C: "century, but"
GRAMMAR CONCEPT APPLIED
Connecting Two Complete Thoughts
When you have two complete thoughts (called independent clauses in grammar terms) - meaning each part has a subject and verb and could stand alone as a sentence - you need proper punctuation to connect them:
Option 1: Comma + Coordinating Conjunction
Use a comma followed by a connecting word (for, and, nor, but, or, yet, so):
- First complete thought: The restaurant was expensive
- Second complete thought: the food was delicious
- Connected properly: The restaurant was expensive, but the food was delicious
- The comma + "but" joins them and shows the relationship (contrast)
Option 2: Semicolon
Use a semicolon when the thoughts are closely related:
- The restaurant was expensive; the food was delicious
What NOT to do:
- Run-on: The restaurant was expensive the food was delicious (no punctuation)
- Comma splice: The restaurant was expensive, the food was delicious (comma alone)
In our question:
- First complete thought: Leibniz wheel calculators were popular in the first half of the twentieth century
- Second complete thought: these ingenious devices were eventually replaced by electronic calculators
- Relationship: Contrast (popular BUT replaced)
- Correct connection: century, but
The comma + "but" properly joins the two thoughts while showing the contrasting relationship between them.
century
("century"):
✗ Incorrect
- This creates a run-on sentence - two complete thoughts placed directly next to each other with nothing connecting them
- "Leibniz wheel calculators were popular in the first half of the twentieth century these ingenious devices..." is grammatically incorrect
- You can't just smash two complete thoughts together without punctuation or a connecting word
century,
("century,"):
✗ Incorrect
- This creates what's called a comma splice - using only a comma to join two complete thoughts
- A comma by itself isn't strong enough to connect two independent ideas
- You need either a comma + a connecting word like "but," or you need stronger punctuation like a semicolon
century, but
✓ Correct
Correct as explained in the solution above.
century that
("century that"):
✗ Incorrect
- This tries to turn the second part into a descriptive phrase about "century"
- But "these ingenious devices were eventually replaced by electronic calculators" doesn't describe the century - it's a separate fact about what happened to the devices
- The logic doesn't work, and it creates an awkward, unclear sentence