A car travels at a speed of 40 km/hr for 2 hours and then decides to slow down to 30 km/hr for the next 2 hours. What is the average speed?
$[3 M a r k s]$

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Solution

D1 = 40 x 2 = 80 km

D2 = 30 x 2 = 60 km
$[1 M a r k]$

Total distance D= D1+D2

D = 80 + 60

D = 140 km
$[1 M a r k]$
We know, $s p e e d = \frac{T o t a l D i s t a n c e t r a v e l l e d}{T o t a l T i m e t a k e n} = \frac{140}{4} = 83.33 m s^{- 1}$

= 140/4

= 35 km/h
$[1 M a r k]$

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A car travels at a speed of 40 km/hr for 2 hours and then decides to slow down to 30 km/hr for the next 2 hours. What is the average speed? [3 Marks]

D1 = 40 x 2 = 80 km D2 = 30 x 2 = 60 km [1 Mark] Total distance D= D1+D2 D = 80 + 60 D = 140 km [1 Mark] We know, speed=TotalDistancetravelledTotalTimetaken=1404=83.33 ms−1 = 140/4 = 35 km/h [1 Mark]

A car travels at a speed of 40 km/hr for 2 hours and then decides to slow down to 30 km/hr for the next 2 hours. What is the average speed?
$[3 M a r k s]$

D1 = 40 x 2 = 80 km

D2 = 30 x 2 = 60 km
$[1 M a r k]$

Total distance D= D1+D2

D = 80 + 60

D = 140 km
$[1 M a r k]$
We know, $s p e e d = \frac{T o t a l D i s t a n c e t r a v e l l e d}{T o t a l T i m e t a k e n} = \frac{140}{4} = 83.33 m s^{- 1}$

= 140/4

= 35 km/h
$[1 M a r k]$