Mr Kor brought his family for a holiday trip to Port Dickson, a distance of 420km from Singapore.

1. On his way up to Port Dickson, he traveled along the trunk road at an average speed of x km/h. Write down expression, in terms of x, for the time taken, in hours, to travel from Singapore to Port Dickson.

2. On return journey to Singapore, he traveled along the North-South Highway and increased the average speed by 20 km/h. Write down an expression, in terms of x, for the time taken, in hours, to travel from Port Dickson to Singapore.

3. If the difference in the time taken between the two journeys was 50 minutes, form an equation in x and show that it reduces to x2+20x-10080=0

4. Solve the equation x2 +20x -10080=0 , giving both answer correct to two decimal places.

5.Find the time taken, correct to the nearest 5 minutes., for the return trip from Port Dickson to Singapore.

Solution:

(1) Time = 420/x hour

(2) Time = 420/(x+20) hour

(3) 420/x - 420/(x+20) = 50/60

We reduce it

x^2 +20x -10080 = 0

(4)

x = 90.90 km/h

(5)

420/(x+20) = 420/(90.90+20) = 227 min