Any rational number with its denominator is in the form of 2^m × 5ⁿ, where m,n are positive integers and are terminating decimals. The examples are shown below:

$\frac{15}{8}=\frac{15}{2\times 2\times 2}=\frac{15}{2^3}=\frac{15\times 5^3}{2^3\times 5^3}=\frac{15\times 125}{8\times 125}=\frac{1875}{1000}=1.875$
$\frac{31}{20}=\frac{31}{2\times 2\times 2}=\frac{31\times 5}{2\times 2\times 5\times 5}=\frac{155}{100}=1.55$
In both the examples, the result is a terminating decimal because terminating decimal is a decimal which can be expressed in a finite number of figures. Hence, a rational number can be expressed as a terminating decimal if the denominator has factors 2 or 5.