A scale drawing has a scale of 1cm:3m explain how the scale can be used to find the actual distance between objects in the drawing

So since 1 m = 100 cm, your ratio using the same units is 1cm: 300cm. Thus, whenever the distance between two objects on the drawing is a number of centimeters, just multiply that number by 300 to get the actual distance in centimeters. Then, divide that number by 100 to get the actual distance in meters.