To find the product of $1.15 and 10, Justin can simply multiply without needing to move the decimal point. However, if he were to conceptualize it using decimal movement, he correctly understands that multiplying by 10 results in moving the decimal point one place to the right.
The correct response is: He knows that 10 is 10 to the power of 1, so he needs to move the decimal point in 1.15 one place to the right.