The rate of consumption of petrol by a vehicle varies directly as the square of the distance covered. If 4 litres of petrol is consumed on a distance of 15km. how far would the vehicle go on 9 litres of petrol?
A. 22\(\frac{1}{2}\)km B. 30km C. 33\(\frac{1}{2}\)km D. 45km
Correct Answer: A
Explanation
R \(\alpha\) D2 R = D2K R = 4 Litres when D = 15cm thus; 4 = 152k 4 = 225k k = \(\frac{4}{225}\) This gives R = \(\frac{4D^2}{225}\) Where R = 9litres equation gives 9 = \(\frac{4D^2}{225}\) 9 x 225 = 4d2 D2 = \(\frac{9 \times 225}{4}\) D = \(\sqrt{9 \times 225}{4}\) = \(\frac{3 \times 15}{2}\) = 22\(\frac{1}{2}\)km
