Lots of help from HRW for learning how to use ratios to make indirect measurements and use scale drawings to solve problems. The Guided Practice section has examples, video tutorials and interactive practice with answers available. The Practice and Problem Solving section has two parts. The first part offers practice with a complete video explanation for the type of problem with just a click of the video icon. The second part offers practice with the solution for each problem only a click of the light bulb away.