Asked: If p, q, r, s and t are positive integers such that \(x = 2^p3^q\) and \(y = 2^r3^s5^t\), can the fraction \(\frac{x}{y}\) be expressed as decimal with only finite number of non zero digits ?
\(\frac{x}{y} = \frac{2^p3^q}{2^r3^s5^t} = 2^{p-r}3^{q-s}5^{-t}\)
(1) \(\frac{x}{y} >1\)
\(\frac{x}{y} = \frac{2^p3^q}{2^r3^s5^t} = 2^{p-r}3^{q-s}5^{-t} > 1\)
If q >= s ; the fraction \(\frac{x}{y}\) be expressed as decimal with only finite number of non zero digits
But if q<s ; the fraction \(\frac{x}{y}\) can not be expressed as decimal with only finite number of non zero digits
NOT SUFFICIENT
(2) \(\frac{q}{s} > 1\)[/quote]
\(\frac{x}{y} = \frac{2^p3^q}{2^r3^s5^t} = 2^{p-r}3^{q-s}5^{-t} > 1\)
If q >= s ; the fraction \(\frac{x}{y}\) be expressed as decimal with only finite number of non zero digits
But if q<s ; the fraction \(\frac{x}{y}\) can not be expressed as decimal with only finite number of non zero digits
q/s > 1 => q > s
The fraction \(\frac{x}{y}\) be expressed as decimal with only finite number of non zero digits
SUFFICIENT
IMO B