document.write( "Question 961099: The product of Mary's age in years on her last birthday and her age now in complete months is 1800. How old was Mary on her last birthday? \n" ); document.write( "

Algebra.Com's Answer #587442 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

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The product of Mary's age in years on her last birthday and her age now in complete months is 1800.
\n" ); document.write( " How old was Mary on her last birthday.
\n" ); document.write( "Let x = her age on her last birthday in yrs
\n" ); document.write( "then
\n" ); document.write( "12x = her age in months on her last birthday
\n" ); document.write( ":
\n" ); document.write( "let m = number of months from her last birthday. (her present age)
\n" ); document.write( "then
\n" ); document.write( "12x + m = her present age in months
\n" ); document.write( ":
\n" ); document.write( "x * (12x + m) = 1800
\n" ); document.write( "12x^2 + mx = 1800
\n" ); document.write( "mx = -12x^2 + 1800
\n" ); document.write( "m = $\"%28%28-12x%5E2%2B1800%29%29%2Fx\"$
\n" ); document.write( "m = -12x + $\"1800%2Fx\"$
\n" ); document.write( "only integer solution that makes sense
\n" ); document.write( "x=12 yrs on last birthday, then m = 6 months
\n" ); document.write( "Present age: 12*12 + 6 = 150 months
\n" ); document.write( ":
\n" ); document.write( "Check
\n" ); document.write( "age last birthday: 12 yrs, present age 150 months; 12 * 150 = 1800
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