6×9

6×9, read as six by nine, is a compact notation used in mathematics and in various practical contexts. In standard base-10 arithmetic, six multiplied by nine equals 54. The expression is a simple example of basic multiplication and can be used to illustrate area calculations for rectangles with sides 6 and 9 units, or for sizing in design.

Base representations: The same numerical value can be written differently in other numeral systems. For example, in base 13, 54 decimal is written as 42, since 4×13 + 2 = 54. This is a mathematical fact unrelated to any particular culture.

Common uses: 6×9 is a widely used trim size for books, especially trade paperbacks and self-published titles, because the aspect ratio is 2:3 (6:9 simplifies to 2:3). The typical dimensions in metric are approximately 15.24 cm by 22.86 cm. The size influences layout, margins, and typography.

Practical applications: In audio equipment, 6x9 refers to a speaker dimension (6 inches by 9 inches) common in car audio. These speakers are often mounted in rear decks and door panels and can be configured as two-way or three-way systems.

Cultural note: The phrase has appeared in popular culture. A well-known reference in The Hitchhiker's Guide to the Galaxy involves a joke that six multiplied by nine equals forty-two, in base-13, creating a playful nod to the series' Answer to the Ultimate Question.