9.2.3 Speed and Acceleration, PT3 Focus Practice


Question 7:
Karen drives her car from town P to town Q at an average speed of 80 km/h for 2 hours 15 minutes. She continues her journey for a distance of 90 km from town Q to town R and takes 45 minutes.
Calculate the average speed, in km/h, for the journey from P to R.

Solution:
From P to Q: Average speed=80 km/h Time taken = 2 hours 15 minutes    = 2 1 4  hours Distance=average speed×time taken Distance =80×2 1 4    =80× 9 4    =180 km From Q to R: Distance =90 km Time taken = 45 minutes    =  3 4  hour Average speed from P to R = 180+90 2 1 4 + 3 4 Total distance Total time = 270 3 =90 km/h


Question 8:
Diagram below shows the distance from Town P to Town Q and Town Q to Town R.
(a) Rahim rode his bicycle from Town P at 9.00 a.m. and took 2 hours to reach Town Q.
What is the speed, in km/h, of the bicycle?

(b) Rahim took 30 minutes rest at Town Q and continued his journey to Town R three times faster than his earlier speed.
State the time he reached Town R.


Solution:
(a)
The speed of the bicycle from Town P to Town Q = Distance Time = 10 2 =5 km/h

(b)
Speed= Distance Time Rahim took 30 minutes rest at Town Q. Time taken when his journey to Town R three times faster than his earlier speed. = 25 5×3 = 5 3 =1 2 3  hours =1 hour 40 minutes  2 3 ×60 =40 minutes Total time taken from Town P to Town Q and Town Q to Town R =2 hours +30 minutes+1 hour 40 minutes =4 hour 10 minutes The time he reached Town R at 1.10 p.m.




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