Three different numbers have a product that is greater than

\(a < b < c\)

\(abc > 1000\)

\(? = c\)

\(\left( 1 \right)\,\,{\rm{primes}}\,\,\,\left\{ \matrix{\\
\,{\rm{Take}}\,\,\left( {a,b,c} \right) = \left( {7,11,13} \right)\,\,\,\,\left[ {abc = 1001} \right]\,\,\,\,\, \Rightarrow \,\,\,? = 13 \hfill \cr \\
\,{\rm{Take}}\,\,\left( {a,b,c} \right) = \left( {7,11,17} \right)\,\,\,\,\, \Rightarrow \,\,\,\,\,? = 17 \hfill \cr} \right.\)

\(\left( 2 \right)\,\,abc < 1310\,\,\,\,\,\,\left\{ \matrix{\\
\,\left( {{\mathop{\rm Re}\nolimits} } \right){\rm{Take}}\,\,\left( {a,b,c} \right) = \left( {7,11,13} \right)\,\,\,\, \Rightarrow \,\,\,? = 13 \hfill \cr \\
\,\left( {{\mathop{\rm Re}\nolimits} } \right){\rm{Take}}\,\,\left( {a,b,c} \right) = \left( {7,11,17} \right)\,\,\,\,\left[ {abc = 1309} \right]\,\,\,\,\, \Rightarrow \,\,\,? = 17 \hfill \cr} \right.\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,\,\left( {\rm{E}} \right)\)


We follow the notations and rationale taught in the GMATH method.

Regards,
Fabio.