souvik101990
A store sells only two types of shirts - branded and non-branded. All the branded shirts are priced at $60 per unit and all the non-branded shirts are priced at $20 per unit. On a certain day, the store sold a total of 30 shirts. What is the number of branded shirt that the store sold on that day?
1) The store sold more than 20 branded shirts on that day.
2) On that day, the total sales from shirts were between $1604 and $1674.
\(30\,{\text{units}}\,\,\,\left\{ \begin{gathered}\\
\,B\,\,{\text{branded}}\,{\text{,}}\,\,{\text{\$ 60}}\,\,{\text{each}} \hfill \\\\
\,N\,\,{\text{non - branded}}\,{\text{,}}\,\,{\text{\$ 20}}\,\,{\text{each}} \hfill \\ \\
\end{gathered} \right.\)
\(? = B\)
\(\left( 1 \right)\,\,B > 20\,\,\left\{ \begin{gathered}\\
\,{\text{Take}}\,\,\left( {B,N} \right) = \left( {21,9} \right)\,\,\,\, \Rightarrow \,\,\,\,? = 21 \hfill \\\\
\,{\text{Take}}\,\,\left( {B,N} \right) = \left( {22,8} \right)\,\,\,\, \Rightarrow \,\,\,\,? = 22 \hfill \\ \\
\end{gathered} \right.\,\,\,\,\, \Rightarrow \,\,\,\,\,{\text{INSUFF}}.\)
\(\left( 2 \right)\,\,1604 < 60B + 20\left( {30 - B} \right) < 1674\,\,\,\,\,\,\left[ \$ \right]\)
\(1604 < 40B + 600 < 1674\)
\(25 \cdot 40 + 4 = 1004 < 40B < 1074 = 26 \cdot 40 + 34\)
\(25 + \frac{4}{40} < B < 26 + \frac{34}{40}\,\,\,\,\, \Rightarrow \,\,\,\,\,? = B = 26\,\,\,\,\, \Rightarrow \,\,\,\,\,{\text{SUFF}}.\)
This solution follows the notations and rationale taught in the GMATH method.
Regards,
Fabio.