Final answer:
To calculate the total amount Robert paid for the used automobile, we added the 5% sales tax to the original cost. The sales tax is $75 ($1500 x 0.05), resulting in a total payment of $1575.
Step-by-step explanation:
Robert purchased a used automobile for $1500, and we are asked to calculate the total amount he paid after including a 5% sales tax. To find the sales tax amount, we need to convert the percentage to a decimal by dividing it by 100 and then multiplying it by the cost of the automobile.
The calculation is as follows:
1500 x 0.05 = $75
Adding the sales tax to the original cost of the automobile gives us Robert's total payment:
$1500 + $75 = $1575
Therefore, Robert paid a total of $1575 for the used automobile after including the sales tax.