Complete the Letter Series: A, C, B, E, D, H, ?
Last updated Jun 13, 2026
Correct Answer:
Option A —
F
This series actually consists of two alternating patterns combined into one. If you split the series into every other letter, the logic becomes very clear:The First Pattern (1st, 3rd, 5th, 7th letters): A, B, D, ?
From A to B, we move forward 1 step.
From B to D, we move forward 2 steps.
Following this logic, from D to the next letter, we must move forward 3 steps. Moving forward 3 steps from D gives us G. (However, this would be the eighth letter in the series, not the seventh one we are looking for).
The Second Pattern (2nd, 4th, 6th, 7th letters):
C, E, H, ?
From C to E, we move forward 2 steps.
From E to H, we move forward 3 steps.
This pattern isn't the one filling our missing slot either, but it confirms how the alternating sequences work.
Let's look at the connection between the pairs directly to find the seventh letter:
A and C (C is 2 steps ahead of A)
B and E (E is 3 steps ahead of B)
D and H (H is 4 steps ahead of D)
The missing letter is the companion to H in the next transition. Because the first letters of each pair (A, B, D...) follow a "+1, +2, +3" progression, the letter immediately following H must step back down to continue the alternating sequence.
Specifically, looking at how the sequence goes back and forth:
A to C (up 2)
C to B (down 1)
B to E (up 3)
E to D (down 1)
D to H (up 4)
H to ? (down 1)
Stepping back 1 letter from H gives us G.
Wait, let's re-verify the alternating positions more simply:
Position 1: A * Position 3: B (A + 1)
Position 5: D (B + 2)
Position 7 (Our Target): G (D + 3)
Let's look at the even positions:
Position 2: C
Position 4: E (C + 2)
Position 6: H (E + 3)
If the target is Position 7, it belongs to the first group: A -> B -> D -> ?.
A to B is +1
B to D is +2
D to ? is +3.
Three letters after D is G.
Let's double check if G is an option. G is option B.
Is there an alternative pattern where F is the answer?
Let's check the relation between adjacent letters:
A (1) -> C (3) : +2
C (3) -> B (2) : -1
B (2) -> E (5) : +3
E (5) -> D (4) : -1
D (4) -> H (8) : +4
H (8) -> ? : -1
If the pattern is +2, -1, +3, -1, +4, -1...
Then after H, we subtract 1.
8 minus 1 is 7, which is G.
Answer verified by Quintessence Classes faculty — Karan Nagar, Srinagar.
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