PrepSwift Sequences tested, but missing concept

GRE Quant Problem Solving
1

I just stumbled over a question in Mean and Median’s Relationship exercises which tests arithmetic sequences, even though they have never been mentioned anywhere else.

I pretty much trust PrepSwift to provide me with critical Quant concepts, but this one seems to be missing? Will it be introduced at some point?

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2

Well,

  • the question is the same thing as “what is the mean of integers of 1, 4, …, 100 \times 3 - 2”, which takes ideas from the “# of Multiples in Interval” and “Sum of Multiples in Interval” videos. So there is nothing that is out of scope in this question.
  • However, you’re right in that the word “sequence” should be defined, and the answer is that there are missing videos on sequences and series, which is the only material that is on the GRE that is not on PrepSwift (you need to use the long videos for that). That’s something we need to add. As a result, I’m also hesitant to “define” sequences only for this question, as we have occasionally done elsewhere on PrepSwift.
3

Regarding

Blockquotehe question is the same thing as “what is the mean of integers of 1, 4, …, 100×3−2
”, which takes ideas from the “# of Multiples in Interval” and “Sum of Multiples in Interval” videos. So there is nothing that is out of scope in this question.

I see where the question was coming from, but this is different than just finding the sum of multiples as there are no common multiples of 4 or 7 other than 1 and 0. So not sure how to derive the sequences formula naturally from this.

I’m very surprised (and slightly shocked) that sequences are not being taught on PrepSwift. I also can’t find any traces of sequences on the quant flashcards, there is nothing. Are there any other concepts on PrepSwift missing? I’m asking as this is my main source of truth when it comes to quant concepts learning.

For covering sequences, which long videos are you referring to specifically?

4

You have

1,4,7, ...
=(3 - 2), (6 - 2), (9 - 2)

In other words, notice how we can split this into a “multiple of 3 - constant” case?

Your criticism on this is valid. The reason they were not included is that they don’t show up on the ETS Math Review (which is usually our canonical reference on “what’s on the test”), but that they are on the test. We do have to add them though, but procrastination from the team members’ side…

No.

Just search the site for “sequences”; there are a few videos on our side covering this topic. Just pick any one.