A.2.3—Substitution into algebraic equations

Substitution replaces each symbol with a measured or given value. First identify the quantity each symbol represents, then convert units so the equation remains dimensionally valid.

Write the equation, insert values with units, calculate and round at the end. If a value is a rate, preserve its time basis rather than treating it as a total.

For distance = rate × time, 2 m s⁻¹ for 30 s gives 60 m; using 30 min without conversion would inflate the answer by a factor of 60.

A calculator can evaluate the wrong equation perfectly; definition and unit checks come first.