document.write( "Question 174973: I need help!!
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document.write( "- A car travelled 470 km from Sudbury to Brandford in 5 hours. For part of the trip, the car travelled at 100 km/h. For the rest of the trip, it travelled at 90 km/h. How far did the car travel at each speed?\r
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document.write( "I tried
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document.write( "x+y=5
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document.write( "100x+90=470\r
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document.write( "100x+100y=500
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document.write( "100x+90y=470\r
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document.write( "= 10y = 30
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document.write( "x=2 y=3
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document.write( "but I only got half marks. Where did I go wrong and what was the answer? \n" );
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Algebra.Com's Answer #130041 by Electrified_Levi(103)![]() ![]() ![]() You can put this solution on YOUR website! Hi, Hope I can help, \n" ); document.write( ". \n" ); document.write( "I need help!! \n" ); document.write( "- A car travelled 470 km from Sudbury to Brandford in 5 hours. For part of the trip, the car travelled at 100 km/h. For the rest of the trip, it travelled at 90 km/h. How far did the car travel at each speed? \n" ); document.write( ". \n" ); document.write( "We will start fresh \n" ); document.write( ". \n" ); document.write( "First we need to know a formula \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "A car travelled 470 km from Sudbury to Brandford in 5 hours. For part of the trip, the car travelled at 100 km/h. For the rest of the trip, it travelled at 90 km/h. How far did the car travel at each speed? \n" ); document.write( ". \n" ); document.write( "This problem is a little tricky, since the car is going two speeds, instead of just one, we also have two different times. \n" ); document.write( ". \n" ); document.write( "This will mean we will have two unknowns, we can find the other unknowns with the information we have \n" ); document.write( ". \n" ); document.write( "A car travelled 470 km from Sudbury to Brandford in 5 hours. For part of the trip, the car travelled at 100 km/h. For the rest of the trip, it travelled at 90 km/h. How far did the car travel at each speed? \n" ); document.write( ". \n" ); document.write( "Remember that \n" ); document.write( ". \n" ); document.write( "We can say that the time it took when the car went 90 km/h, the time it took would be \n" ); document.write( ". \n" ); document.write( "We can say that how long it took when the car went 100 km/h, the time it took would be \n" ); document.write( ". \n" ); document.write( "It is the same concept with the distances \n" ); document.write( ". \n" ); document.write( "one distance would be \n" ); document.write( ". \n" ); document.write( "the second unknown distance would be \n" ); document.write( ". \n" ); document.write( "We can now find equations to this problem \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Equation 1 \n" ); document.write( ". \n" ); document.write( "if the car went 100 km/h ( rate ) \n" ); document.write( ". \n" ); document.write( "if the car took \n" ); document.write( ". \n" ); document.write( "These two multiplied together will equal a distance \n" ); document.write( ". \n" ); document.write( "Now we would put the words into a formula, \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Now we will use the other distance, time, and rate, to find the second equation \n" ); document.write( ". \n" ); document.write( "If the car went 90 km/h ( rate ) \n" ); document.write( ". \n" ); document.write( "If the car took \n" ); document.write( ". \n" ); document.write( "If the car drove \n" ); document.write( ". \n" ); document.write( "Now replace \"r\", \"t\" and \"d\" with the other veriables \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Now we can put these two equations side by side \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "To make it easier, we will simplify the two equations \n" ); document.write( ". \n" ); document.write( "Equation 1, \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( "(remember the signs \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Equation 2, we will just multiply the \"90\" and \"x\" \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Now we can start solving for the two unknowns \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "This is a system of equations, the easiest way to solve this system is by substitution \n" ); document.write( ". \n" ); document.write( "Since \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "(remember \"x\" is the time in hours), we can replace \"x\" with \"3\" in the second equation, to find \"y\" \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "x = 3 \n" ); document.write( ". \n" ); document.write( "y = 270 \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "Here are the simplified equations with the numbers \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "If we look at the formula, \n" ); document.write( ". \n" ); document.write( " \n" ); document.write( ". \n" ); document.write( "This means that the car went 200 km at 100 km/h, and it went 100 km/h for 2 hours \n" ); document.write( ". \n" ); document.write( "The car went 270 km at 90 km/h, and it went 90 km/h for 3 hours \n" ); document.write( ". \n" ); document.write( "The distances add up to the total distance, as well as the time with the total time \n" ); document.write( ". \n" ); document.write( "The car went 200 km at 100 km/h \n" ); document.write( ". \n" ); document.write( "The car went 270 km at 90 km/h \n" ); document.write( ". \n" ); document.write( "Hope I helped, Levi \n" ); document.write( " \n" ); document.write( " |