In the letter pair series IM, JO, KQ, LS, which pair of letters should come next to correctly complete the pattern?

Introduction / Context:
This question deals with letter pairs in a series, where each term consists of two alphabetic characters. These pairs often advance according to different rules for the first and second letters. Many exam questions of this type use simple arithmetic progressions on alphabet positions. Recognising and separating the patterns for each position is the key to answering quickly and accurately.

Given Data / Assumptions:
- Given series of pairs: IM, JO, KQ, LS, ? - Each term has two letters: a first letter and a second letter. - We assume the pattern is consistent from the first pair to the last. - Alphabet positions: A = 1, B = 2, ..., Z = 26.

Concept / Approach:
The standard technique is to separate the series into two independent sequences: one formed by all the first letters and another formed by all the second letters. We then convert each letter to its number, examine the step size between consecutive terms, and identify a progression. Often the first and second letters follow different arithmetic patterns, such as +1 for one sequence and +2 for the other. Once both patterns are identified, we can compute the next pair of letters and map them back from numbers to characters.

Step-by-Step Solution:
Step 1: Separate first and second letters. First letters: I, J, K, L. Second letters: M, O, Q, S. Step 2: Work on the first letter sequence. I = 9, J = 10, K = 11, L = 12. The positions increase by +1 each time. So the next first letter after L (12) is 13, which corresponds to M. Step 3: Work on the second letter sequence. M = 13, O = 15, Q = 17, S = 19. Here, positions increase by +2 each time. So the next second letter after S (19) is 21, which corresponds to U. Step 4: Combine both results. The next pair is M (first letter) and U (second letter), giving MU.

Verification / Alternative check:
We can verify quickly by writing the numeric pattern directly: First letters: 9, 10, 11, 12, 13 (simple +1 series). Second letters: 13, 15, 17, 19, 21 (simple +2 series). The consistency of these progressions confirms that MU is the only pair that fits. Any other pair would disturb at least one of these arithmetic progressions. Thus, the derived answer MU is both logically and numerically consistent with the overall pattern of the series.

Why Other Options Are Wrong:
A) NV would require the first letter to jump from L (12) to N (14), breaking the +1 rule for first letters. C) MY would give M for the first letter correctly, but Y (25) for the second letter disrupts the +2 pattern from S (19). D) NT adjusts both letters incorrectly and does not match either established progression.

Common Pitfalls:
Some students mistakenly look for a single pattern on the combined pair rather than analysing each position separately. Others may miscount letter positions if they rush, especially around the middle of the alphabet. A reliable strategy is to always write down A to Z with corresponding numbers for quick reference. Additionally, double check the step size in each sequence; very often they are small such as +1, +2, or +3. Once that habit is developed, letter pair series become straightforward in reasoning exams.

Final Answer:
The pair of letters that correctly completes the series IM, JO, KQ, LS, ? is MU.