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

one state would change   like louisiana to texas. thats a change

explanation:

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%