Question

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

(x+5)km for every litre of petrol. If car A uses 4 litres of
petrol more than car B in covering the 400km, determine
the number of litres of petrol used by car B for the journey​

Answer 1

Answer: 16 litres

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