document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=288305>Question 288305</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I noticed that when I interchanged the digits of my father’s age, I got my own age. When I was born, his age was between twenty and thirty years. What was my father’s age when I was born?<BR>\n" );
document.write( "(A) 20 (B) 26 (C) 27 (D) 30 (E) None of these </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #208970 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=208970\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> I noticed that when I interchanged the digits of my father’s age, I got my own age. When I was born, his age was between twenty and thirty years. What was my father’s age when I was born?<BR>\n" );
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document.write( "Let father's age be 10t+u where t is the ten's digit and u is the unit's digit.<BR>\n" );
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document.write( "My age 10a+b now<BR>\n" );
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document.write( "Equations etc.<BR>\n" );
document.write( "10u+t = 10a+b.<BR>\n" );
document.write( "20 < (10t+u)-(10a+b) < 30<BR>\n" );
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document.write( "Working with the inequality you get:<BR>\n" );
document.write( "Substitute for 10a+b to get:<BR>\n" );
document.write( "20 < (10t+u)-(10u+t) < 30<BR>\n" );
document.write( "20 < 9t-9u < 30<BR>\n" );
document.write( "20/9 < t-u < 30/9<BR>\n" );
document.write( "2.22< t-u < 3.33<BR>\n" );
document.write( "But t and u are positive whole numbers<BR>\n" );
document.write( "So t-u = 3<BR>\n" );
document.write( "t = u+3<BR>\n" );
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document.write( "Ans: D<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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document.write( "(A) 20 (B) 26 (C) 27 (D) 30 (E) None of these<BR>\n" );
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