Alphabet test and letter series for SSC CHSL

Alphabet questions are the cheapest marks in SSC CHSL reasoning, but only if you know the letter positions without counting on your fingers. A candidate who has to count "A, B, C…" to find the 19th letter spends 15 seconds on what should take two, and makes an off-by-one error roughly every tenth time.

This guide covers the positions, the counting rules and the question types built on them. The same positions power coding–decoding and letter analogies, so the time you spend here pays off three times.

How it is asked

• Position questions: "Which letter is 8th from the right?" or "Which letter is 5th to the right of the 12th letter from the left?"
• Reverse alphabet: the same questions after the alphabet is written backwards.
• Letter series: "C, F, I, L, ?" or "BDF, HJL, NPR, ?"
• Letter pairs in a word: "How many pairs of letters in DEFINE have as many letters between them as in the alphabet?"
• Repeating patterns: fill the blanks in a string such as "a _ b a a _ a _ b".

Positions you should know by heart

Three facts make this fast:

• EJOTY marks 5, 10, 15, 20 and 25. To find the 18th letter, go to T (20) and step back two: R.
• Position from the right = 27 − position from the left. R is 18th from the left and 9th from the right.
• Opposite letters add to 27: A–Z, B–Y, C–X, D–W, E–V, F–U, G–T, H–S, I–R, J–Q, K–P, L–O, M–N. A short way to remember the middle: "M–N sit together".

The counting rules

When counting from the left end of the normal alphabet:

• "k-th to the right of" a letter means add k to its position.
• "k-th to the left of" a letter means subtract k.
• The n-th letter from the right is at position 27 − n from the left.
• Letters between two letters: the difference in positions minus 1. Between G (7) and P (16) there are 16 − 7 − 1 = 8 letters.

For a reversed alphabet, the n-th letter from the left is the n-th letter from the right of the normal alphabet, so its normal position is 27 − n. Work out the position in the reversed list first, then convert once at the end. Converting at every step is where mistakes happen.

Letter series and groups

Letter series use the same rules as number series, applied to positions. Write the positions under the letters and check differences first.

• Constant gap: C, F, I, L → +3 → O.
• Growing gap: A, C, F, J, O → +2, +3, +4, +5 → +6 → U.
• Backward: Z, W, T, Q → −3 → N.
• Groups: in BDF, HJL, NPR each group moves on six letters and each letter inside a group is two apart.

If the gap takes you past Z, wrap round: after Z comes A again. Z (26) + 3 = 29, and 29 − 26 = 3, which is C.

Six worked questions

Q1. Which letter is 7th to the right of the 15th letter from the left? (a) U (b) T (c) W (d) V
15 + 7 = 22, which is V. Answer: (d) V.

Q2. Which letter is 4th to the left of the 10th letter from the right? (a) M (b) L (c) N (d) O
The 10th from the right is at 27 − 10 = 17 from the left (Q). Four to the left: 17 − 4 = 13, which is M. Answer: (a) M.

Q3. If the alphabet is written in reverse order, which letter is 8th to the right of the 5th letter from the left? (a) M (b) N (c) O (d) L
Stay inside the reversed list: 5 + 8 = 13th from the left of the reversed alphabet. Convert once: 27 − 13 = 14, which is N. You can check by writing the reversed list: Z Y X W V U T S R Q P O N, and the 13th is N. Answer: (b) N.

Q4. A, C, F, J, O, ? (a) T (b) W (c) V (d) U
Positions 1, 3, 6, 10, 15. Gaps 2, 3, 4, 5, so the next gap is 6: 15 + 6 = 21, which is U. Answer: (d) U.

Q5. BDF, HJL, NPR, ? (a) SUW (b) TUV (c) TVX (d) UWY
The first letters are B, H, N (2, 8, 14), moving on six each time, so the next starts at 20 (T). Inside each group the letters are two apart: T, V, X. Answer: (c) TVX.

Q6. How many pairs of letters in the word DEFINE have as many letters between them in the word as in the alphabet? (a) 1 (b) 2 (c) 3 (d) 4
Check each pair. D and E are next to each other in the word and in the alphabet. D and F have one letter between them in the word (E) and one in the alphabet (E). E and F are adjacent in both. No other pair works: for example, F and I sit next to each other in the word but have two letters between them in the alphabet (G, H). Answer: (c) 3.

Common traps

Practice

1. Which letter is 11th from the right? (a) P (b) O (c) Q (d) K
2. Which letter is 6th to the left of the 20th letter from the left? (a) M (b) O (c) N (d) P
3. What is the opposite letter of G? (a) S (b) R (c) U (d) T
4. D, H, L, P, ? (a) S (b) T (c) U (d) V
5. B, E, J, Q, ? (a) Z (b) Y (c) X (d) W
6. CE, GI, KM, ? (a) NP (b) PR (c) OQ (d) OP
7. How many letters are there between G and P in the English alphabet? (a) 7 (b) 8 (c) 9 (d) 10
8. Fill the blanks so the string repeats a pattern: a _ b a a _ a _ b (a) bab (b) abb (c) baa (d) aba

Answers:

1. (a) P. 27 − 11 = 16, which is P.
2. (c) N. 20 − 6 = 14, which is N.
3. (d) T. G is 7; 27 − 7 = 20, which is T.
4. (b) T. Positions 4, 8, 12, 16 go up by 4, so the next is 20.
5. (a) Z. Positions 2, 5, 10, 17 have gaps 3, 5, 7; the next gap is 9, and 17 + 9 = 26.
6. (c) OQ. The first letters are C, G, K (3, 7, 11), so the next is 15 (O). Each pair is two apart, so O is followed by Q.
7. (b) 8. 16 − 7 − 1 = 8: H, I, J, K, L, M, N, O.
8. (d) aba. The string becomes aab aab aab, a repeating unit of "aab".

What to do next

• Write the position table from memory each morning for five days, then test yourself on random letters.
• Learn the 13 opposite pairs until you can answer any one in under two seconds.
• Solve 20 position questions a day, always converting to "from the left" first.
• Use the positions straight away in coding–decoding, and compare letter series with number series, which follow the same checking order.