Question

Is 43.123456789 rational or not. If it is rational, and of the form $\frac{p}{q}$, what can you say about the prime factors of q?

Answer 1

The number 43.123456789 has a terminating decimal expansion. Thus, it is a rational number of the form $\frac{p}{q}$.
And, q is of the form $2^m\times 5^n$ where m and n are non-negative integers.