PRACTISE NOW 11 Ex
15
Mr Lee drove from City P to City Q, which are 600 km apart. During his return journey,
his average speed was increased by 7 km/h and the time taken was 15 minutes less.
() If he drove at an average speed of x km/h on his journey from City P to City Q,
formulate an equation in x and show that it reduces to x2 + 7x – 16 800 = 0.
(ii
) Solve the equation x² + 7x - 16 800 = 0, giving both your answers correct to
2 decimal places.
(iii) Find the time taken for the return journey.