document.write( "Question 1142129: 3 litre of oil and 30 litre of petrol cost R45 while 7 litre and 15 litre of petrol cost R40.Calculate the price of the oil. \n" ); document.write( "
Algebra.Com's Answer #762803 by ankor@dixie-net.com(22740)\"\" \"About 
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let a = the price of oil
\n" ); document.write( "let b = the price of petrol
\n" ); document.write( ":
\n" ); document.write( "write an equation for each statement
\n" ); document.write( ":
\n" ); document.write( "3 litre of oil and 30 litre of petrol cost R45
\n" ); document.write( "3a + 30b = 45
\n" ); document.write( ":
\n" ); document.write( "while 7 litre and 15 litre of petrol cost R40.
\n" ); document.write( "7a + 15b = 40
\n" ); document.write( ":
\n" ); document.write( "Calculate the price of the oil.
\n" ); document.write( "Use elimination, multiply the 2nd equation by 2, subtract the 1st equation
\n" ); document.write( "14a + 30b = 80
\n" ); document.write( " 3a + 30b = 45
\n" ); document.write( "---------------subtraction eliminates b, find a
\n" ); document.write( "11a + 0 = 35
\n" ); document.write( "a = 35/11
\n" ); document.write( "a = $3.18 for oil
\n" ); document.write( ":
\n" ); document.write( "Use the 1st equation to find b,
\n" ); document.write( "3(3.18) + 30b = 45
\n" ); document.write( "9.54 + 30b = 45
\n" ); document.write( "30b = 45 - 9.54
\n" ); document.write( "30b = 35.46
\n" ); document.write( "b = 35.46/30
\n" ); document.write( "b = $1.18 for petrol
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "See if these awkward solutions check out in the 2nd equation
\n" ); document.write( "7(3.18) + 15(1.18) =
\n" ); document.write( "22.26 + 17.70 = 39.96 ~ 40 \n" ); document.write( "
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