Khan Academy and Purplemath offer lessons on ratios. Khan Acadaemy offers nine video lessons and two interactive solvable problems based on the ratio lessons. Purplemath has seven Web pages of detailed information regarding ratios.
Khan Academy differs from Purplemath in the format of the lessons. Purplemath is entirely text- and picture-based, while Khan Academy's lessons are video-based. The lessons are available 24/7, and individuals use them at their own pace. After completing the ratio lesson, the user can advance to the next lesson or fast forward to higher levels of mathematics. Khan Academy and Purplemath offer the full range of mathematics lessons, from early math to college level calculus.