Algebra: A Combined Approach (4th Edition)

$\frac{1231}{10}$
The decimal given is 123.1, which has one decimal, so the denominator of the fraction will have one zero (10). In other words, the decimal 123.1 goes to the tenths place, so 123.1 represents 1,231 tenths, which can be written as $\frac{1231}{10}$.