What is asked
A random series of letters, digits and symbols, e.g. R 4 % T 7 K # 2 M @ 9 B, followed by 3-5 questions. The site generates these with computed answers; use these notes for the method.
Common question types
- "Which element is 5th to the right of the 9th from the left?"
- "How many symbols are immediately preceded by a number and immediately followed by a letter?"
- "If all the symbols are removed, which element will be 6th from the right?"
- "Four of the following five are alike based on their positions" (e.g. T7K, 2M@, ...: each group skips a fixed number of elements).
- "What should come next in the series based on the positions: R%7, T K 2 ...?"
Position formula
| Question | Formula (series of N elements) |
|---|---|
| k-th from left | position k |
| k-th from right | position N - k + 1 |
| a-th to the right of k-th from left | position k + a |
| a-th to the left of k-th from right | position N - k + 1 - a |
Convert everything to a position from the left, then count once. Right adds, left subtracts.
Counting conditions
- Underline the element type asked about (for example every symbol).
- For each underlined element check the neighbour on the stated side ("immediately preceded" = the element just to its left, "immediately followed" = just to its right).
- Tick only when both conditions hold.
Worked example
Series: R 4 % T 7 K # 2 M @ 9 B (N = 12). The 9th from the left is M. 2nd to the right of M is position 11, which is 9. The symbols are % (preceded by 4, followed by T), # (preceded by K) and @ (preceded by M). Only % is immediately preceded by a number and immediately followed by a letter, so the count is 1.
Group-based questions
Questions such as "4 % T : 7 # 2 :: K @ B : ?" or "four of the following five groups are alike" are built from positions. Note the position of each element of the first group and find the gap pattern (for example, element, +2, +3). Apply the same gaps to the next group. A quick check: write the positions as numbers (2-3-4, 5-7-8 ...) rather than the elements, and the odd group stands out immediately.
Time target
20-30 seconds per question. Write position numbers above the series once; it pays off across all questions.