CCAT Logical Reasoning: Letter Series

Logical Reasoning: Letter series

AV Krishnan
4 min readMar 15, 2021

Here, a number of groups of letters will be given. The next group of letters will need to be figured out.

Q1: What would be the next group of letters in the following series?

a … b … c … d … ?

Answer: It is clear that the letters are in alphabetical order. Hence, the next letter is e.

Q2: What would be the next group of letters in the following series?

b … d … f … h … ?

Answer: Here, the letters are in alphabetical order, but with one letter skipped after each. So, the next letter will be j.

The above examples are quite simple. In the CCAT, you will come across groups of letters, like:

ab … cd … ef … gh … ?

In these cases, each letter in a term could follow a different rule. Here:

The first letters of each term are: a … c … e … g … ? The missing letter is clearly i (one letter skipped after each one)

The second letters are: b … d … f … h … ? The missing letter is j (again one letter skipped after each)

So, the missing term is ij

Q3: What would be the next group of letters in the following series?

cp … en … gl … ij … ?

Answer:

Here, the first series is c, e, g, i. The letters are in order, skipping one letter after each. Hence, the next letter would be k.

The second series is p, n, l, j. The letters are in reverse order, with one letter skipped after each. Hence, the missing letter is h.

Hence, the missing term is kh

NOTE: You should keep the letters a to z written out neatly on a sheet of paper prior to appearing in the CCAT. This will help you spot patterns, and make calculations faster.

Letters “wrap” around. Hence, the letter after ‘z’, if needed, would be ‘a’. Similarly, the letter before ‘a’ would be ‘z’.

Now, try these:

Q-1: What would be the next group of letters in the following series?

xeb, vfd, thg, rki, …?

pol, pgl, sol, pnl, pno

Q-2: What would be the next group of letters in the following series?

udkm … tejm … sfim … rghm

qigm, qhfm, qhgm, rgfm, phgm

Q-3: What would be the next group of letters in the following series?

wgfi … yfgm … aehq … cdiu … ?

fchy, fbkz, ecjy, ecky, ebjz

Solutions:

Q-1: What would be the next group of letters in the following series?

xeb, vfd, thg, rki, …?

Answer Options: pol, pgl, sol, pnl, pno

Answer-1:

Let’s consult the alphabet (which we had written earlier, prior to the start of the test):

abcdefghijklmnopqrstuvwxyz

Let’s look at the first letter of each term:

x, v, t, r, ?

Each successive letter is formed by taking the current letter and moving backward in the alphabet, skipping one. So the missing letter is two letters before r, which is p.

Now for the second letter: e, f, h, k, ?

The difference between f and e is 0 letters

The difference between h and f is 1 letter (g comes in between)

The difference between k and h is 2 letters (I, j come in between)

Hence the difference between k and the next letter would be 3 letters, and would be k, (l, m, n), o

The first two letters of the answer are therefore po, and on scanning thru the answer choices, we see that only one option (the first one, pol, starts with po). Hence, we can mark pol as correct and move on.

For the sake of completion, let’s look at the third letter: b, d, g, i, ?

The difference between successive letters is 1, 2, 1…. Therefore, the next difference will be 2, and the next letter will be i (j, k) l. This confirms that pol is the correct answer.

Q-2: What would be the next group of letters in the following series?

udkm … tejm … sfim … rghm

Answer Options: qigm, qhfm, qhgm, rgfm, phgm

Answer-2:

Let’s go letter by letter:

First letter of each term: u, t, s, r, … q (preceding letter)

d, e, f, g, … h (next letter)

k, j, i, h, … g (preceding letter) [we can stop here]

m, m, m, … m (same letter is repeated)

So, the answer is qhgm.

Q-3: What would be the next group of letters in the following series?

wgfi … yfgm … aehq … cdiu … ?

Answer Options: fchy, fbkz, ecjy, ecky, ebjz

Answer-3:

Following the same strategy as the first two questions, going letter by letter:

First letter of each term: w, y, a, c, … e (next letter, skipping a letter)

g, f, e, d, … c (preceding letter)

f, g, h, i, … j (next letter) [we can stop here]

i, m, q, u, … y (skip 3 letters to get the next letter)

So, the answer is ecjy.

Coming up next: CCAT Spatial Reasoning — Series completion with shapes or symbols

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AV Krishnan

I am an Electrical Engineer (from IIT Kharagpur) and a software developer by passion. I try to distill and impart whatever I know with utmost clarity.