When adding or subtracting numbers in relation to significant figures, your final answer will be based on what? 1. least number of significant figures in the questions 2. least number of decimal places and significant figures in the question 3. least number of decimal places in the question 4. most decimal places in the question

3. Least number of decimal places in the question

Explanation:

When adding or subtracting values, you must round your answer to the same "place" as the measurement with its last significant figure furthest to the left.  

That is, you round off to the same number of decimal places as the measurement with the fewest decimal places.

1 is wrong. It is the rule for multiplication and division

2 is wrong. It includes both the rule for multiplication and division and the rule for addition and subtraction.

4 is wrong. The rule requires the fewest decimal places

Medicinal chemistry involves the creation and refinement of molecules for the purpose of creating or improving drugs.