Bar Model for Problems on Ratio Rate Direct Proportion

Use this applet to understand arithmetic problems related to rate, ratio, direct proportion.[br][br]Do you know why when we do arithmetic involving ratio, rate and direct proportion[br]we always divide to a single unit of the item on the left before multiplying to get the answer?[br][br]After manipulating and exploring the Bar Model applet below, do you get the concept now?

Information: Bar Model for Problems on Ratio Rate Direct Proportion