document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=980379>Question 980379</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A father is 60 years old and his son is half his age.  How old was the boy when his father was four times his age? </SPAN>\n" );
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document.write( "F=father's age; S=son's age; x=years ago father's age=4 times son's age<BR>\n" );
document.write( ".<BR>\n" );
document.write( "F=2S<BR>\n" );
document.write( "60=2S<BR>\n" );
document.write( "30=S Son is 30 years old.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "F-x=4(S-x)<BR>\n" );
document.write( "60-x=4(30-x)<BR>\n" );
document.write( "60-x=120-4x<BR>\n" );
document.write( "3x=60 <BR>\n" );
document.write( "x=20 Father was 4 times as old as son 20 years ago.<BR>\n" );
document.write( ".<BR>\n" );
document.write( "Son is now 30, 20 years ago he was 30-20=10 years old.<BR>\n" );
document.write( "ANSWER: The son was 10 years old when his father was four times his age.<BR>\n" );
document.write( "(Father is now 60, so Father was 60-20=40 years old.) </SPAN>\n" );
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