document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=393625>Question 393625</A>: <I><SPAN STYLE=\"word-break: break-all;\"> At present, the sum of the parents' ages is twice the sum of the children's ages. five years ago, the sum of the parents's ages was four times the sum of the children's ages. Fifteen years hence, the sum of the parents' ages will be equal to the sum of the children's ages.How many children are there? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #279326 by </B><A HREF=/tutors/aboutme.mpl?userid=mananth><B>mananth(16946)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mananth><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/cgi-bin/show-face.mpl?user=mananth><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=279326\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> At present, the sum of the parents' ages is twice the sum of the children's ages. five years ago, the sum of the parents's ages was four times the sum of the children's ages. Fifteen years hence, the sum of the parents' ages will be equal to the sum of the children's ages.How many children are there?<BR>\n" );
document.write( "...<BR>\n" );
document.write( "let number of children be x<BR>\n" );
document.write( "let sum of childrens' age = y<BR>\n" );
document.write( "sum of parents' age = z<BR>\n" );
document.write( "..<BR>\n" );
document.write( "z=2y<BR>\n" );
document.write( "5 years ago<BR>\n" );
document.write( "z-10 = 4(y-5x) ( four times their age 5 years ago.)(x children so less 5x)<BR>\n" );
document.write( "2y-10=4y-20x<BR>\n" );
document.write( "2y-20x=-10<BR>\n" );
document.write( "/2<BR>\n" );
document.write( "y-10x=-5.....................1<BR>\n" );
document.write( "15 years later ( 2 parents so add 30 )<BR>\n" );
document.write( "z+30= 15x+y<BR>\n" );
document.write( "2y+30=15x+y<BR>\n" );
document.write( "15x-y=30......................2<BR>\n" );
document.write( "add both<BR>\n" );
document.write( "5x=25<BR>\n" );
document.write( "/5<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28highlight%28x=+5%29%29 ALIGN=MIDDLE  ALT=\"%28highlight%28x=+5%29%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >  Number of children<BR>\n" );
document.write( "plug value of x in (1)<BR>\n" );
document.write( "15*5-y=30<BR>\n" );
document.write( "75-y=30<BR>\n" );
document.write( "y=70-30<BR>\n" );
document.write( "y=45 sum of childrens' age<BR>\n" );
document.write( "...<BR>\n" );
document.write( "z= 2y = 90 sum of parents' age<BR>\n" );
document.write( "..<BR>\n" );
document.write( "m.ananth@hotmail.ca </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );