Translucent Lab: Multiplying Fractions with Overlays
Lay one fraction's shading over another's on the same square, and the doubly-shaded overlap is their product.
A part... of a part
In everyday language, the word “of” often means multiply. Half of a quarter pizza, a third of two thirds of a chocolate bar — both are fraction multiplication problems in disguise. Each one starts with a fraction of a whole, then takes only a fraction of that piece.
Shading two ways over the same square
Draw a square and shade vertical stripes across three of its four columns to show 3⁄4. On the very same square, shade horizontal stripes across two of its three rows to show 2⁄3. Some cells now have both stripe directions — they are shaded twice. That doubly-shaded region is the product, 3⁄4 × 2⁄3.
Why you multiply straight across
Splitting the square into columns and rows creates a grid of small equal cells — the total number of cells is columns × rows, which becomes the new denominator. The cells shaded in both directions are the overlap — shaded columns × shaded rows — which becomes the new numerator.
- Multiply the numerators: 2 × 3 = 6.
- Multiply the denominators: 3 × 4 = 12.
- The product is 6/12, which simplifies by dividing top and bottom by 6.
- Half a batch means multiplying the recipe amount by 1/2: 1/2 × 3/4.
- Multiply the numerators: 1 × 3 = 3.
- Multiply the denominators: 2 × 4 = 8.
Check your understanding
- Multiplying two fractions means finding a part of a part — a fraction of a fraction.
- Overlay two shaded fractions on the same square; the doubly-shaded overlap is their product.
- Multiply numerators together and denominators together: a/b times c/d equals (a times c)/(b times d).
- Simplify the product to lowest terms when possible.
- Unlike whole numbers, multiplying two fractions less than 1 gives a result smaller than either fraction.