If a diagram has a scale of 1:100, that means that the real thing is 100 times larger. To find how long the real thing is, that means that we need to multiply the length on the diagram by 100. 100 * 15 is 1500. But, that is 1,500 cm. To convert it into meters, we need to divide by 100. That's because there's 100 centimeters in every meter. 1500/100 is 15, which means that the actual length of the car park is 15 meters.
