Question

Is -1.987 a rational number

Answer 1

A rational number is a number which can be written a ratio of two integers.

In decimal form, a rational number is any number which either terminates or repeats after the decimal point. Since -1.987 terminates after the 7, it is a rational number.

Answer 2

Yes, a finite decimal can be expressed as the ratio of two integers, so is a rational number. Here

$-1.987 = \dfrac{-1987}{1000}$

Technically we might say that -1.987 is not strictly a rational number because it doesn't have the form of two integers separated by a fraction bar. It does however equal a rational number.

Yes is the answer being sought here.