a school ruler has metric on one side and customary units on the other. if the ruler is 12 inches long how many centimeters long is the ruler

And the conversion for the inch to the centimeter is 1 inch = 2.54 cm exactly. So, in the same vCalc conversion equation (Length Conversion), if you input 1 inch, you get out 2.54 cm. So, he rephrased answer to your question is: there are 30.48 centimeters on a standard 12 inch ruler.