document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1209628>Question 1209628</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please help me answer this question\r<BR>\n" );
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document.write( "The cost of petrol rises by 2cents a litre.<BR>\n" );
document.write( "Last week a man bought 20 litres at the old price<BR>\n" );
document.write( "This week he bought 10 litres at the new price<BR>\n" );
document.write( "All together it costed $9.20<BR>\n" );
document.write( "What was the old price for 1 litre<BR>\n" );
document.write( "Let x be the old price\r<BR>\n" );
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document.write( "Solution\r<BR>\n" );
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document.write( "I tried saying 20 times x plus 10 times x plus two is equal to 920cents<BR>\n" );
document.write( "Then I got 20x plus 10x plus 20 is equal to 920 cents <BR>\n" );
document.write( "Then I said 10x plus 20x is equal to 30x = 920 cents minus 20<BR>\n" );
document.write( "Then I sais 30x + 900 divided by 30\r<BR>\n" );
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document.write( "I then got the answer x = 0,30 cents<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #852103 by </B><A HREF=/tutors/aboutme.mpl?userid=johnsss><B>johnsss(2)</B></A><img src=\"/images/stars/iconNewId_16x16.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=johnsss><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=johnsss><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=852103\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> To solve the problem about the price of petrol, we can use a weighted average approach (similar to the concept of nota ponderada, or \"weighted average\"). Here's the step-by-step solution:<BR>\n" );
document.write( "Source: https://mipromedio.co/blog/como-calcular-promedio-universitario/<BR>\n" );
document.write( "Let x be the old price per litre in cents.\r<BR>\n" );
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document.write( "The new price per litre is x + 2 cents.\r<BR>\n" );
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document.write( "The man bought 20 litres at the old price and 10 litres at the new price, with a total cost of 920 cents.\r<BR>\n" );
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document.write( "We can set up the equation:\r<BR>\n" );
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document.write( "20<BR>\n" );
document.write( "𝑥<BR>\n" );
document.write( "+<BR>\n" );
document.write( "10<BR>\n" );
document.write( "(<BR>\n" );
document.write( "𝑥<BR>\n" );
document.write( "+<BR>\n" );
document.write( "2<BR>\n" );
document.write( ")<BR>\n" );
document.write( "=<BR>\n" );
document.write( "920<BR>\n" );
document.write( "20x+10(x+2)=920<BR>\n" );
document.write( "Simplify the equation:\r<BR>\n" );
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document.write( "20<BR>\n" );
document.write( "𝑥<BR>\n" );
document.write( "+<BR>\n" );
document.write( "10<BR>\n" );
document.write( "𝑥<BR>\n" );
document.write( "+<BR>\n" );
document.write( "20<BR>\n" );
document.write( "=<BR>\n" );
document.write( "920<BR>\n" );
document.write( "20x+10x+20=920<BR>\n" );
document.write( "30<BR>\n" );
document.write( "𝑥<BR>\n" );
document.write( "+<BR>\n" );
document.write( "20<BR>\n" );
document.write( "=<BR>\n" );
document.write( "920<BR>\n" );
document.write( "30x+20=920<BR>\n" );
document.write( "Subtract 20 from both sides:\r<BR>\n" );
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document.write( "30<BR>\n" );
document.write( "𝑥<BR>\n" );
document.write( "=<BR>\n" );
document.write( "900<BR>\n" );
document.write( "30x=900<BR>\n" );
document.write( "Solve for x:\r<BR>\n" );
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document.write( "𝑥<BR>\n" );
document.write( "=<BR>\n" );
document.write( "900<BR>\n" );
document.write( "30<BR>\n" );
document.write( "=<BR>\n" );
document.write( "30<BR>\n" );
document.write( " cents<BR>\n" );
document.write( "x= <BR>\n" );
document.write( "30<BR>\n" );
document.write( "900<BR>\n" );
document.write( "​<BR>\n" );
document.write( " =30 cents<BR>\n" );
document.write( "So, the old price per litre was 30 cents.\r<BR>\n" );
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document.write( "This approach uses the concept of a weighted average because we are calculating the total cost by weighting the quantities (20 litres at the old price and 10 litres at the new price).<BR>\n" );
document.write( "Source: https://mipromedio.co/blog/como-calcular-promedio-universitario/<BR>\n" );
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