document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=252232>Question 252232</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Suppose that the electricity bill is determined only by multiplying the number of kilowatt hours used by the cost per kilowatt hour. Last February Ben’s electric bill was $50. This February the number of kilowatt hours used was 20% higher and the rate per kilowatt hour was 8% lower. To the nearest percent, select the percentage by which his electric bill has changed.\r<BR>\n" );
document.write( "\n" );
document.write( "A. 12% increase B. 10% increase C. 0% D. 10% decrease E. 12% decrease </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #184064 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=184064\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> c = cost per kilowatt hour<BR>\n" );
document.write( "k = number of kilowatt hours.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "you get:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "c*k = 50\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "that was last february.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "this february the bill is:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( ".92*c*1.2*k = ?????\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "this is the same as:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( ".92*1.2*c*k = ?????\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "we know that c*k is equal to $50.00, so the equation becomes:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( ".92*1.2*50 = ?????\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "this becomes:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( ".92*1.2*50 = 55.2\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "this years bill should be $55.20\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "55.2/50 = 1.104 - 1 = .104 * 100% = 10.4%.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "rounded to the nearest integer, this because a 10% increase which would be selection B.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "example:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "assume the cost per kilowatt hour was 20 cents / 100 = $.20\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "if the bill was 50, then the kilowatt hours were 250.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "drop the cost by 8% to get c = .2 * (1-.08) = .2 * .92 = .184 per kilowatt hour.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "raise the number of kilowatt hours by 20% to get 250 * (1 + .2) = 250 * 1.2 = 300 kilowatt hours.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "figures for last february were:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "c = .2<BR>\n" );
document.write( "k = 250\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "figures for this february are:\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "c = .184<BR>\n" );
document.write( "k = 300\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( ".184 * 300 = 55.2\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "cost for last february was $50.00<BR>\n" );
document.write( "cost for this february is $55.20\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( "55.2 / 50 = 1.104 - 1 = .104 * 100% = 10.4% rounded to the nearest integer = 10%.\r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " \r<BR>\n" );
document.write( "<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );