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A certain number of marbles are to be removed from a box

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A certain number of marbles are to be removed from a box

by AAPL » Mon Jan 28, 2019 3:54 am

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A certain number of marbles are to be removed from a box containing only solid-colored red, yellow, and blue marbles. How many more yellow marbles than red marbles are in the box before any are removed?

1) To guarantee that a red marble is removed, the smallest number of marbles that must be removed from the box is 14.
2) To guarantee that a yellow marble is removed, the smallest number of marbles that must be removed from the box is 8.

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by fskilnik@GMATH » Mon Jan 28, 2019 4:21 am

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AAPL wrote:Manhattan Prep

A certain number of marbles are to be removed from a box containing only solid-colored red, yellow, and blue marbles. How many more yellow marbles than red marbles are in the box before any are removed?

1) To guarantee that a red marble is removed, the smallest number of marbles that must be removed from the box is 14.
2) To guarantee that a yellow marble is removed, the smallest number of marbles that must be removed from the box is 8.
$$? = Y - R\,\,\,\,\,\left( {{\text{yellow,}}\,{\text{red and}}\,\,{\text{blue}}\,\,{\text{marbles}}\,\,{\text{only}}} \right)$$
$$\left( 1 \right)\,\,Y + B = 13\,\,\,\left\{ \matrix{
\,{\rm{Take}}\,\,\left( {Y,R,B} \right) = \left( {12,1,1} \right)\,\,\,\, \Rightarrow \,\,\,? = 11 \hfill \cr
\,{\rm{Take}}\,\,\left( {Y,R,B} \right) = \left( {12,2,1} \right)\,\,\,\, \Rightarrow \,\,\,? = 10 \hfill \cr} \right.$$
$$\left( 2 \right)\,\,R + B = 7\,\,\,\left\{ \matrix{
\,{\rm{Take}}\,\,\left( {Y,R,B} \right) = \left( {12,6,1} \right)\,\,\,\, \Rightarrow \,\,\,? = 6 \hfill \cr
\,{\rm{Take}}\,\,\left( {Y,R,B} \right) = \left( {13,6,1} \right)\,\,\,\, \Rightarrow \,\,\,? = 7 \hfill \cr} \right.$$
$$\left( {1 + 2} \right)\,\,\,\left\{ \matrix{
\,Y + B = 13 \hfill \cr
\,R + B = 7 \hfill \cr} \right.\,\,\,\,\,\,\mathop \Rightarrow \limits^{\left( - \right)} \,\,\,\,\,\,? = Y - R = 13 - 7\,\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{\rm{SUFF}}.$$

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Fabio.
Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
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