14.2.1 Ratio, Rates and Proportions II, PT3 Focus Practice


Question 1:
The distance from town A to town B is 120 km. A car leaves town A for town B at 11.00 a.m. The average speed is 80 km h-1 .
At what time does the car arrive at town B.

Solution:
Time taken= distance travelled average speed = 120 km 80  km h 1 = 3 2  hours = 1 hour 30 minutes 1 hour 30 minutes after 11.00 a.m. is 12.30 p.m.


Question 2:
Kenny drives his car from town P to town Q at a distance of 180 km in 3 hours.
Faisal takes 30 minutes less than Kenny for the same journey.
Calculate the average speed, in km/h, of Faisal’s car.

Solution:
Time taken by Faisal = 3 hours30 minutes = 3 hours 1 2  hour = 2 1 2  hours Average speed of Faisal’s car = distance travelled time taken = 180 km 2 1 2  hours =72 km/h


Question 3:
Rafidah drives her car from town L to town M at an average speed of 90 km/h for 2 hours 40 minutes. She continues her journey for a distance of 100 km from town M to town N and takes 1 hour 20 minutes.
Calculate the average speed, in km/h, for the journey from L to M.

Solution:
Distance=average speed×time taken Distance from L to M=90×2 40 60   =90×2 2 3   =90× 8 3   =240 km Total distance from L to N=240+100   =340 km Total time taken = 2 hours 40 minutes + 1 hour 20 minutes    = 4 hours Average speed for the journey from L to N= 340 km 4 h    =85 km/h


Question 4:
Susan drives at an average speed of 105 km/h from town F to town G.
The journey takes 3 hours.
Susan takes 30 minutes longer for her return journey from town G to town F. Calculate the average speed, in km/h, for the return journey.

Solution:
Distance from F to G = 105 km/h×3 hours =315 km Average speed for return journey = distance travelled time taken = 315 km 3 1 2  hours =90 km/h


Question 5:
Table below shows the distances travelled and the average speeds for four vehicles.

Vehicle Distance (km) Average speed (km/h)
A 230 115
B 250 100
C 170 85
D 245 70
Which vehicles took the same time to complete the journey?

Solution:
Time taken for vehicle A= 230 115 =2 hours Time taken for vehicle B= 250 100 =2 1 2  hours Time taken for vehicle C= 170 85 =2 hours Time taken for vehicle D= 245 60 =3 1 2  hours

Thus, the vehicles A and C took the same time to complete the journey.

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