document.write( "Question 616419: i buy 20 pencils at a certain price and 30 other more expensive pencils.the pencils cost me 90p.had i bought 30 of the cheaper pencils and the 20 of the dearer , i should have saved 5p.find the cost of of one of the dearer pencils. \n" ); document.write( "

Algebra.Com's Answer #387678 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+a+\"$ = price of one of the cheaper pencils
\n" ); document.write( "Let $\"+b+\"$ = price of one of the dearer pencils
\n" ); document.write( "given:
\n" ); document.write( " $\"+20a+%2B+30b+=+90+\"$
\n" ); document.write( "(1) $\"+2a+%2B+3b+=+9+\"$
\n" ); document.write( "and
\n" ); document.write( " $\"+30a+%2B+20b+=+90+-+5+\"$
\n" ); document.write( " $\"+30a+%2B+20b+=+85+\"$
\n" ); document.write( "(2) $\"+6a+%2B+4b+=+17+\"$
\n" ); document.write( "Multiply both sides of (1) by $\"+3+\"$
\n" ); document.write( "and subtract (2) from (1)
\n" ); document.write( "(1) $\"+6a+%2B+9b+=+27+\"$
\n" ); document.write( "(2) $\"+-6a+-+4b+=+-17+\"$
\n" ); document.write( " $\"+5b+=+10+\"$
\n" ); document.write( " $\"+b+=+2+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(1) $\"+2a+%2B+3b+=+9+\"$
\n" ); document.write( "(1) $\"+2a+%2B+3%2A2+=+9+\"$
\n" ); document.write( "(1) $\"+2a+=+9+-+6+\"$
\n" ); document.write( "(1) $\"+2a+=+3+\"$
\n" ); document.write( "(1) $\"+a+=+1.5+\"$
\n" ); document.write( "1.5p is the price of one of the cheaper pencils
\n" ); document.write( "2p is the price of one of the dearer pencils
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+6a+%2B+4b+=+17+\"$
\n" ); document.write( "(2) $\"+6%2A1.5+%2B+4%2A2+=+17+\"$
\n" ); document.write( "(2) $\"+9+%2B+8+=+17+\"$
\n" ); document.write( "(2) $\"+17+=+17+\"$
\n" ); document.write( "You can check (1) \n" ); document.write( "

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