Question

A) Car A travels x km for every litre of petrol while car B travels

Answer 1

Answer:   16 litres

Step-by-step explanation:

A:   1l          x  km

B:   1l         x+5   km

Running 400 km   A used   400/x  litres

Running  400 km  B used  400/(x+5)  litres

400/x- 400/(x+5)= 4

400*(x+5)- x*400-4*x*(x+5)=0

400*x+2000-400*x-4*x²-20*x=0

2000-4*x²-20*x=0     difide by 4 both sides of equation

500-x²-5*x=0

Lets solve the equation using discriminant:

D=5²-(-1)*4*500=2025

sqrt(D)=45

x1= (5+45)/(-2)= -25          x2=(5-45)/(-2)=20

x1=-25     x2=20

x1<0 so is not the solution of the problem ( number of litres can't  be negative)

So A uses  litr per x=20 km     and B uses 1 litr per 20+5=25 km

Running 400 km B uses 400/25=16 litres