Array Index Calculation

Array index calculation: how to solve

Array index questions usually ask you to find the position of an element, the value stored at a position, or the result of a small index-based expression. The key idea is to follow the indexing rule exactly and compute carefully.

1. Identify what is being asked

• Index of a value: find where a value appears in the array.
• Value at an index: read the entry at the given position.
• Index expression: evaluate any arithmetic first, then use the result as the index.

2. Watch the starting point

Some arrays are numbered from 0, while others start from 1. Use the numbering system given in the exercise. A common mistake is to count one position too far.

3. Simplify the calculation

If the index is an expression, simplify it step by step before selecting an element. For example, compute additions, subtractions, or parentheses first, then use the final number as the index.

4. Check your answer

Make sure the index is valid for the array length and that the selected value matches the position you counted. If the exercise asks for a simplified final answer, write only the final number or element, not the intermediate steps.

Quick check

Count positions carefully and verify that your result fits the array’s indexing rule.