Sachar includes many equations in Fuzzy Mud. The math represents the exponential growth of the dangerous, mutated ergonyms—and the inexorable speed at which the earth’s population is increasing. The equations symbolize both natural and manmade threats to humankind and, as a literary device, help increase suspense and tension, as Fitzman’s creation increasingly escapes scientific control. This makes the sci-fi threat more credible, paralleling the increasingly likely real-life disasters that overpopulation will generate.

In addition, Sachar refers to human interactions and emotions as different kinds of equations. Math was Marshall’s best subject before Chad arrived. When Chad isn’t in class, Marshall’s confidence in working the math equations returns, only to disappear again when Mrs. Thaxton arrives. The equations reflect Marshall’s emotions—his initial self-assurance and subsequent fear about his lie: “The equations remained on the whiteboard, unsolved” (73)—much as Marshall’s emotions remain conflicted. Meanwhile, Tamaya thinks of her life, in part, as an equation. She feels that because of her parents’ divorce, she’s living two “half lives” that “added together didn’t quite equal a whole life” (77). Human feelings can be described in mathematical terms but don’t have mathematical solutions.