document.write( "Question 915237: the tens didigit of a certain two digit number is twice the units digit. if the numberis multiplied by the sum of it's digit, the product is 63. find the numebr \n" ); document.write( "

Algebra.Com's Answer #555480 by josmiceli(19441) $\"\"$ $\"About$

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Let $\"+t+\"$ = the tens digit
\n" ); document.write( "Let $\"+u+\"$ = the units digit
\n" ); document.write( "(1) $\"+t+=+2u+\"$
\n" ); document.write( "---------------
\n" ); document.write( "The number is:
\n" ); document.write( " $\"+10t+%2B+u+\"$
\n" ); document.write( "(2) $\"+%28+10t+%2B+u+%29%2A%28+t+%2B+u+%29+=+63+\"$
\n" ); document.write( "(2) $\"+10t%5E2+%2B+u%2At++%2B+10u%2At+%2B+u%5E2++=+63+\"$
\n" ); document.write( "(2) $\"+10t%5E2+%2B+11u%2At+%2B+u%5E2++=+63+\"$
\n" ); document.write( "---------------
\n" ); document.write( "Substitute (1) into (2)
\n" ); document.write( "(2) $\"+10%2A%282u%29%5E2+%2B+11u%2A2u+%2B+u%5E2++=+63+\"$
\n" ); document.write( "(2) $\"+40u%5E2+%2B+22u%5E2+%2B+u%5E2+=+63+\"$
\n" ); document.write( "(2) $\"+63u%5E2+=+63+\"$
\n" ); document.write( "(2) $\"+u+=+1+\"$
\n" ); document.write( "and
\n" ); document.write( "(1) $\"+t+=+2%2A1+\"$
\n" ); document.write( "(1) $\"+t+=+2+\"$
\n" ); document.write( "The number is 21
\n" ); document.write( "------------------
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+%28+10t+%2B+u+%29%2A%28+t+%2B+u+%29+=+63+\"$
\n" ); document.write( "(2) $\"+21%2A%28+2%2B+1+%29+=+63+\"$
\n" ); document.write( "(2) $\"+21%2A3+=+63+\"$
\n" ); document.write( "(2) $\"+63+=+63+\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );