challenging math algebra question. (need some help) no answers

Quote:

Originally Posted by coffeegirly99

here goes : (any help appreciated)

a) when driven in town, a car runs at x kilometres on each litre of petrol
(i) find in terms of x , the number of litres of petrol used when the car is driven 200km in town

number of Liters, V = 200/x

(ii) when driven in town , the car runs (x+4) kilometres on each litre of petrol to go 200km out of town than to go 200km in town. Use this information to write down an equation involving x , and show that is simplifies to :

x^2 + 4x - 160 = 0

the bold statement makes little sense to me ... I understand that in town the car gets x km/L and out of town the car gets (x+4) km/L ... recheck the exact wording.

b) solve the equation x^2 + 4x - 160 = 0

$x^2 + 4x = 160$
$x^2 + 4x + 4 = 160 + 4$
$(x + 2)^2 = 164$
$x + 2 = \pm 2\sqrt{41}$
$x = -2 \pm 2\sqrt{41}$

since x represents km, $x = -2 + 2\sqrt{41}$

c)Calculate total volume of petrol used when the car is driven 40km in down and then 120km out of town.

$V = \frac{40}{x} + \frac{120}{x+4}$

hope this helps