To find the amount of tax on an item, let's analyze the options given:
### Option 1:
Amount of Tax [tex]\(= \text{Original Price} + \text{Total Cost}\)[/tex]
This equation is incorrect because adding the original price and the total cost will not give the tax amount. The total cost includes both the original price and the tax, so adding the original price again would not make sense.
### Option 2:
Amount of Tax [tex]\(= \text{(Total Cost)(Original Price)}\)[/tex]
This equation is incorrect as well. Multiplying the total cost by the original price does not directly relate to how tax is calculated.
### Option 3:
Amount of Tax [tex]\(= \text{(Original Cost)} \times \text{(Tax \%)}\)[/tex]
This is the correct expression. To find the amount of tax, you multiply the original cost of the item by the tax percentage. This way you derive the portion of the original cost that represents the tax.
### Option 4:
Amount of Tax [tex]\(= \text{(Total Cost)} \times \text{(Tax \%)}\)[/tex]
This equation is not correct. Multiplying the total cost (which includes the tax) by the tax percentage would again not help in directly determining the amount of tax.
Therefore, the correct expression to find the amount of tax is:
[tex]\[
\text{Amount of Tax} = (\text{Original Cost}) \times (\text{Tax \%})
\][/tex]
Example: Suppose the original cost of an item is [tex]$1 and the tax percentage is 10\%.
Using the correct formula:
\[
\text{Amount of Tax} = 1 \times 0.1 = 0.1
\]
So, the amount of tax for this example is $[/tex]0.10.
