**Question 6:**

Mei Ling drives her car from Kuantan to Kuala Terengganu for a distance of 170 km for 2 hours. She then continues her journey to Kota Bahru and increases her speed to 100 kmh

^{-1}for 45 minutes.

Calculate the acceleration, in kmh

^{-2}, of the car.

*Solution*:$\begin{array}{l}\text{SpeedfromKuantantoKualaTerengganu}\\ =\frac{170}{2}=85{\text{kmh}}^{-1}\\ \\ \text{Acceleration}\\ =\frac{\text{Finalspeed}-\text{Initialspeed}}{\text{Timetaken}}\\ =\frac{100-85}{\frac{45}{60}}\\ =20{\text{kmh}}^{-2}\end{array}$

**Question 7:**

Diagram shows the distance between

*K*and

*L*.

A car moves from

*K*to

*L*with an average speed of 80 kmh

^{-1}. After rest for 1 hour 30 minutes, the car then returns to

*K.*The average speed of the car from

*L*to

*K*increases 20%. If the car reaches

*K*at 5 p.m., calculate the time the car starts its journey from

*K*.

**$\begin{array}{l}\text{Thetimetakenfrom}K\text{to}L\\ =\frac{160}{80}\\ =2\text{hrs}\\ \\ \text{Theaveragespeedfrom}L\text{to}K\\ =80\times 1.2\\ =96{\text{kmh}}^{-1}\\ \\ \text{Thetimetakenfrom}L\text{to}K\\ =\frac{160}{96}\\ =1\frac{2}{3}\text{hrs}\\ \\ \text{Thetotaltimetakenforthewholejourney}\\ =2+1\frac{1}{2}+1\frac{2}{3}\\ =5\frac{1}{6}\text{hrs}\\ =5\text{hour}10\text{minutes}\end{array}$**

*Solution*:

The car starts its journey from

*K*at 11:50 a.m.

**Question 8:**

Mr Wong is going to watch a movie at 2.30 p.m at a cinema that is 60 km away from his house. He leaves at 1.25 p.m and drives at an average speed of 70 km/h for half an hour. If he drives at an average speed of 75 km/h for the remaining journey, will he arrive before the movie starts?

**Give your reason with calculation.**

*Solution*:$\begin{array}{l}\text{Distancetravelledatthefirst}\frac{1}{2}\text{hour}\\ =70\times \frac{1}{2}\\ =35\text{km}\\ \\ \text{Remainingdistance}=60\text{km}-35\text{km}\\ \text{}=25\text{km}\\ \text{Timetakenfortheremainingjourney}\\ =\frac{25}{75}\\ =\frac{1}{3}\times 60\\ =20\text{minutes}\\ \\ \text{MrWongarrivesat}\\ =1.25\text{p}\text{.m}+30\text{minutes}+20\text{minutes}\\ =2.15\text{p}\text{.m}\\ \\ \text{Yes,hewillarrivebefore2}\text{.30p}\text{.m}\\ \end{array}$

**Question 9:**

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*:$\begin{array}{l}\text{From}P\text{to}Q\text{:}\\ \text{Averagespeed}=80\text{km/h}\\ \text{Timetaken=2hours15minutes}\\ \text{=2}\frac{1}{4}\text{hours}\\ \text{Distance}=\text{averagespeed}\times \text{timetaken}\\ \text{Distance}=80\times 2\frac{1}{4}\\ \text{}=80\times \frac{9}{4}\\ \text{}=180\text{km}\\ \\ \text{From}Q\text{to}R\text{:}\\ \text{Distance}=90\text{km}\\ \text{Timetaken=45minutes}\\ \text{=}\frac{3}{4}\text{hour}\\ \\ \text{Averagespeedfrom}P\text{to}R\\ =\frac{180+90}{2\frac{1}{4}+\frac{3}{4}}\leftarrow \overline{)\frac{\text{Totaldistance}}{\text{Totaltime}}}\\ =\frac{270}{3}\\ =90\text{km/h}\end{array}$