document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=916155>Question 916155</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 1. The average mass of some children in a group was 36kg. When one child who weighed 54kg left the group, the average mass of the remaining children decreased by 2kg. How many children were there in the group at first?<BR>\n" );
document.write( "Teacher's working: <BR>\n" );
document.write( "54kg-36kg=24kg<BR>\n" );
document.write( "18kg divided by 2= 9kg\r<BR>\n" );
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document.write( "2. A group of pupils calculated their average score for a science test. They noted that if anyone scored 14 marks more, their average score would be 90. If anyone scored 4 marks fewer, their average score would be 88. How many pupils are there in the group? <BR>\n" );
document.write( "Teacher's working:<BR>\n" );
document.write( "14+4=18<BR>\n" );
document.write( "18 divided by 2 =9\r<BR>\n" );
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document.write( "I don't understand why in the first question we minus and the second question plus. Can you explain both the questions? Please answer by today because tomorrow is my maths exam!!! Make the solution easy cause I'm still in P5!!<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 #555961 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=555961\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 1)let x be the total mass of the group, then<BR>\n" );
document.write( "x / n = 36, where n is the number of students<BR>\n" );
document.write( "when one child weighing 54kg leaves the group we have<BR>\n" );
document.write( "(x-54) / (n-1) = 36 - 2 = 34<BR>\n" );
document.write( "we have two equations<BR>\n" );
document.write( "x = 36n<BR>\n" );
document.write( "x-54 = 34(n-1)<BR>\n" );
document.write( "x-54 = 34n -34<BR>\n" );
document.write( "substitute for x in second equation<BR>\n" );
document.write( "36n -54 = 34n -34<BR>\n" );
document.write( "subtract 34n from both sides of =<BR>\n" );
document.write( "add 54 to both sides of =<BR>\n" );
document.write( "2n = 20<BR>\n" );
document.write( "n = 10<BR>\n" );
document.write( "there are 10 students<BR>\n" );
document.write( "2) let x be the sum of their scores and y be the average, then<BR>\n" );
document.write( "x / n = y where n is the number of students, also we are given<BR>\n" );
document.write( "(x+14) / n = 90<BR>\n" );
document.write( "(x-4) / n = 88<BR>\n" );
document.write( "from first equation<BR>\n" );
document.write( "x = 90n - 14<BR>\n" );
document.write( "substitute in second equation<BR>\n" );
document.write( "90n - 14 -4 = 88n<BR>\n" );
document.write( "subtract 88n from both sides of =<BR>\n" );
document.write( "2n -18 = 0<BR>\n" );
document.write( "2n = 18<BR>\n" );
document.write( "n = 9\r<BR>\n" );
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