Scientific American presents Math Dude by Quick & Dirty Tips. Scientific American and Quick & Dirty Tips are both Macmillan companies. After all of the fun we’ve had recounting the tales of Knot Dude, ...

Click here to see a step-by-step slideshow. STEP 1 - Draw a square with 5 columns (5 is the denominator of the first fraction) and a square with 4 rows (4 is the denominator of the second fraction).