In this letter and number analogy, GH is related to 78 through alphabet positions; using the same idea, choose the letter pair that corresponds to 1819: GH : 78 :: ? : 1819

Introduction / Context:
This analogy combines letters and numbers using alphabet positions. The pair GH corresponds to 78. You must determine which pair of letters will correspond to 1819 under the same rule. These questions train you to map letters to their ordinal positions in the alphabet and to recognise simple concatenation patterns.

Given Data / Assumptions:

• The alphabet is ordered from A = 1 to Z = 26.
• GH is linked to the number 78.
• The same pattern must generate 1819 from another pair of letters.
• The answer must be one of HG, LM, RS or IJ.

Concept / Approach:
Whenever two letters map to a two digit number, a very common pattern is to use their positions in the alphabet and either add or concatenate them. For GH, we can check whether 7 and 8 are relevant because G is the 7th letter and H is the 8th. If 78 is formed simply by writing these positions side by side, then the mapping is clear. We then look for a letter pair whose positions are 18 and 19, which when concatenated give 1819.

Step-by-Step Solution:
Step 1: Determine the positions of G and H. G is the 7th letter and H is the 8th letter.Step 2: Notice that the number 78 is formed by placing the digits 7 and 8 next to each other, not by adding them.Step 3: Conclude that the rule is: map each letter to its numeric position and then form a two digit or four digit number by concatenating those positions.Step 4: We now want a letter pair that produces 1819. This suggests the first letter has position 18 and the second letter has position 19.Step 5: Identify the 18th letter of the alphabet as R.Step 6: Identify the 19th letter of the alphabet as S.Step 7: Therefore, the pair RS, with positions 18 and 19, corresponds to the number 1819.

Verification / Alternative check:
We can check the other options to confirm that they do not generate 1819. For HG, the positions are 8 and 7, so concatenation would give 87. For LM, the positions are 12 and 13, giving 1213. For IJ, the positions are 9 and 10, giving 910. None of these equals 1819. Only RS correctly maps to 18 and 19, which combined yield 1819, exactly as required.

Why Other Options Are Wrong:
Option A, HG, reverses the letters and therefore the positions, so it cannot produce 1819. Option B, LM, has positions 12 and 13 and would give 1213. Option D, IJ, has positions 9 and 10 and would map to 910. These numbers are entirely different from 1819 and do not fit the analogy pattern established by GH : 78.

Common Pitfalls:
Some candidates mistakenly add positions instead of concatenating them. For example, 7 plus 8 equals 15, which would not match 78, but the presence of 7 and 8 might still mislead them. Others may forget exact letter positions beyond L. The safe approach is to write positions clearly and check whether the example pair supports addition or simple concatenation.

Final Answer:
The letter pair that corresponds to 1819 under the same rule is RS, so option C is correct.