The ultimate pendulum clock, indeed the ultimate mechanical clock of a

Hello...

Let me try to help you with the first question.

1. The passage most strongly suggests that its author would agree with which of the following statements about clocks?

A) Before 1921 no one had designed a clock that used electricity to aid in its timekeeping functions.

B) Atomic clocks depend on the operation of mechanisms that were invented by William Shortt and first used in the Shortt clock.

C) No type of clock that keeps time more stably and accurately than a Shortt clock relies fundamentally on the operation of a pendulum.

D) Subtle changes in the earth's rotation slightly reduce the accuracy of all clocks used in observatories after 1921.

E) At least some mechanical clocks that do not have pendulums are almost identical to Shortt clocks in their mode of operation.

Let us talk about Options C and D.

C - This option would have been extreme if the phrase "than a Shortt Clock" was not present. If that was the case, then it would have talked about all the clocks. However, the phrase "than a Shortt Clock" links it to the passage.

D - The addition of the word "mechanical" to Option D would not make any difference. It still talks about all mechanical clocks - The passage doesn't give information on this.

Hope that resolves the doubt.

All the best,

Thanks,

Saikiran Dudyala
Byju's GMAT Verbal Expert.

dcwanderer30, answer choice (D) ("the earth's rotation varies from one time of year to another") aligns almost perfectly with the following sentence of the passage, found at the end of the second paragraph:


As with any RC question, a good strategy is to 1) ensure you fully understand the question and 2) arrive at four incorrect answer choices and one correct answer choice.

Take another look at the exact wording of the question:


So you know you are looking for something that was first discovered due to the use of the Shortt clock. The other answer choices all deal with topics mentioned in the passage (optical sensing equipment, atomic clocks, etc), but if you stop and ask "did the Shortt clock lead to the discovery of this thing?" you will only come up with answer choice (D). More specifically, "first indications" maps very well to "discovery," and "were gleaned by the use of" tells us that the discovery was due to the use of Shortt clocks.

I hope this helps!

Manukaran, there is not enough information in the passage to prove whether or not your modified answer choice is correct. The first sentence of the passage indicates that the Shortt clock is a pendulum clock, which is one kind of mechanical clock. Your modified answer choice would apply to all mechanical clocks used in observatories after 1921, and the passage simply does not provide information about those other clocks.

In general, changing the wording of an answer choice is not likely to help you much on RC. In a perfect world, you want to build the habit of addressing each answer choice in its exact, original language; playing with hypothetical answer choices isn't the best use of your valuable study time.

I hope this helps!

Question 4 is still not clear. Can someone please help with a detailed explanation on this.

VeritasKarishma egmat generis

It is the other way around.

vacuum chamber => firmly sealed.

The passage tells us that the primary pendulum was housed in a vacuum chamber. It certainly implies that the chamber was firmly sealed (else you cannot maintain vacuum).
So option (B) must be true.

GMATNinja, can you explain the reasoning behind option C in
question 1

Hi BrightOutlookJenn GMATNinja VeritasKarishma! How can we eliminate the wrong answer choices? I did notice the strong language in A - "no one" - and D - "all clocks" - are they wrong because of it? What about E? Many tks!

Hi BrightOutlookJenn GMATNinja VeritasKarishma! Question 2 was tough because it lacked a key word to search for. So, I ended up spending a lot of time in this question. What was your thought process to solve the question? I had to go trough each AC, using process of elimination to finally pick the right answer, but doing so was very time consuming and I couldn't prove the right AC during the test. Tks!

Hi Will2020

For a detail question in RC, you need to be able to put your finger (pretty much literally) on one or more sentences in the passage that PROVE your answer. As you know, extreme language in answer choices makes them suspicious - it raises the bar of how strong the proof must be to support the answer. Your correct inference answer choice must NEVER be based on speculation ("well, it COULD be true, maybe sorta"). If you are speculating, you are not approaching the question effectively.

So on to the answer choices you mentioned:
A - Yes, "no one" is extreme. But what kills this answer choice is what it's about - using electricity to aid in timekeeping functions, and when was the first time that a clock did that. Do we have any idea about the history of this? Absolutely not. The passage isn't talking about this; the focus is more on the accuracy of these Shortt clocks as best-in-class for mechanical clocks.
D - Indeed, "all clocks" is the killer here. Atomic clocks are held up in this passage as seemingly the most accurate clocks, and we have no information about whether changes in the earth's rotation affect them.
E - How could this possibly make sense? The Shortt clock relies on this special setup with the two pendulums that the passage spends a bunch of time telling us about. So how could other clocks with no pendulums be "almost identical" in their mode of operation? It's pretty counter-intuitive, so the author would have needed to dedicate some time to explaining this. Of course, the author did not touch this topic at all (modes of operation that don't use pendulums but are still similar) so this answer is out of scope.

My advice to you is to get much deeper into the passage when you read and tackle the questions. It's like a courtroom trial and you need to be clear about the evidence that is presented to you: what it says, and what it doesn't say. If you just kind of skim through the passage casually, you are not preparing yourself to be effective on these 700-level questions.

Does this help? Let me know.

Best, Jenn

Hi Will2020

The key word is "discovery". A discovery is a big deal and something that should register with you upon reading the passage ... even if you don't remember exactly what they found, you'll likely remember that they found something, and you'll have an idea of where to go back in the passage to look for the exact thing they found.
The two discoveries are announced at the end of the second paragraph and the end of the third paragraph (with more details about that second discovery in the fourth paragraph). The first discovery was using the clocks to learn something new about the Earth, and the second discovery was using the difference between atomic clock time and Shortt clock time to learn something new about Shortt clocks. Once you get clear on these two things, you might narrow down the answer choices to C and D.

However, D is the one we can prove, using the last sentence in the second paragraph "The first indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks." as evidence.

Will2020
Yes, (A) and (D) are wrong because of the use of "no one" and "all" but not because these words indicate strong language. It is because these words are not supported by the passage. Note that the answer (C) uses similar "strong language" - no type of clock.
But it is supported by the passage:
"The ultimate pendulum clock, indeed the ultimate mechanical clock of any kind, was invented by a British engineer, William Shortt."
As for (E), the passage gives us nothing about "mechanical clocks that do not have pendulums".

I agree that question 1 was tricky but question 2 was not. I read the passage, read question 1, felt a little lost and had to read the passage again. After the second read though, question 1 was obvious since nothing else was supported by the passage at all. Also, answer to question 2 was right there.

"The first indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks."
This told me that Shortt clocks told us about seasonal variations.

So question 2 .. led to the discovery that ...
just reminded me that shortt clocks told us about seasonal variations. One run of the answers and it was obviously (D).

When the questions are not specific data questions and more "which of the following is implied?" or "what would the author agree with?" variety, it might be a good idea to read the passage carefully - twice. Even if you spend 4-5 mins doing that, your answers would stare right at you.

Hey VeritasKarishma

In questions number 2, option E says, "pendulums can be synchronized with one another electronically" and this looks quite persuading as well. How did you eliminate this option?

2 claims to reject this option:
1. Electronically ( chips, digital etc.) and electrically ( electric current) are not same things. So this option is not even close.
2. Even we replace electromechanically with electronically , still answer would not be correct. As highlighted by GMATNINJA in this post, the question is : led to the discovery of what thing? Pendulums can be synchronized effectively that's why they used them to synchronize. How can this information leads to discovery? In this context , it is saying in same way that we can paint using a brush . So after paint is completed, it could not lead to discovery that a brush can paint

Vegita - Note that the passage doesn't say that synchronised pendulums were not used before in any other instrument. So we don't know whether the Shortt clock was the first one to do it.
Also, we need identify a "discovery" that was made with the "use" of Shortt clock. So what was it that existed before but had not been discovered till Shortt clocks started getting used?

The passage tells us:
"The first indications of seasonal variations in the earth's rotation were gleaned by the use of Shortt clocks."

So there are seasonal variations in earth's rotation and these were discovered by the use of Shortt clocks - makes sense.

Thanks VeritasKarishma ma'm for making this tough para looks so easy. I found that the answers are staring directly. I was looking at wrong place before and trying to make sense out of nothing.

Please give a suggestion
Sometimes specific lines could not be located in the passage when try to solve question.
Example: While solving Q2
2. According to the passage, the use of Shortt clocks led to the discovery that
I looked in 1st para and 2nd para where any information about shortt clocks was present.
I shortlisted A, B and D in my first reading

The went to .After replacing the electromechanical linkage with modern optical sensing equipment, he measured the Shortt clock's rate against the observatory's atomic clocks for a month. to reject A.
went to "In addition to causing the familiar ocean tides, both the sun and the moon raise tides in the solid body of the earth.The effect is to raise and lower the surface of the earth by about 30 centimeters. " to reject C
Then arrive at the text after hunting in the passage. Finally extracted the meaning.


While reading, many times I don't extract specific information. Hence while solving questions, in which we need to find out which option is true , if could not locate the right sentence for specific information then tends to get it wrong.
My Query:
How to improve efficiency of such questions and get to the right text instead of fishing the key words in the passage.
What can be done while reading the passage that we come back to the right content.

Please suggest .VeritasKarishma GMATNinja

Try to read the passage not because you have to but because you want to. For example, if it were a recent press release related to your profession, you would want to read it to find out what has happened, how it impacts you, your work etc.
When you read a passage, think what the author is saying to you. Imagine someone saying those statements to you and try to understand them. When we glaze over passages with a closed mind, we read without actually comprehending much. It's not a "mark the keywords" exercise. It is reading comprehension so the questions will try to find whether you understood what the author was saying.
Practice this and over time you will see a difference.