SOLUTION: When driven out of town the car runs x+4 km on each liter of petrol. It uses 5 litres less petrol to go 200 km out of town than to go 200 km in town. Use this information to write

Question 875169: When driven out of town the car runs x+4 km on each liter of petrol. It uses 5 litres less petrol to go 200 km out of town than to go 200 km in town. Use this information to write down an equation involving x and show that it simplifies to x2+4x-160=0
Answer by josgarithmetic(39799) (Show Source): You can put this solution on YOUR website!
Uniform rates involving volume of fuel and distance. FUEL EFFICIENCY is the rate and the route in one direction has some different conditions than in the other direction.

, unit is kilometers per liter. Same as .

WAY__________Rate__________Distance__________Volume
Out_________x+4_____________200______________v-5
In___________r______________200______________v

We can use the fundamental relation rule to express r better:

WAY__________Rate__________Distance__________Volume
Out_________x+4_____________200______________v-5
In___________200/v__________200______________v

Nothing more is possible from this data. Clearly the two routes differ because the fuel volumes are not equal for the same path or road; and the fuel efficiency rates cannot be equal: .
More information is needed. Do you see a way to obtain a quadratic equation in only x?
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