John is driving a car at 30 km/hr speed. He drove for half an hour and then he changed his speed to 60 km/hr and drove for another half an hour. What is the total distance covered by John and also find its average speed? [5 MARKS]

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Solution

Distance Covered: 2 Marks
Average Speed: 2 Marks
Steps: 1 Mark

John drove the first 30 minutes at 30 km/hr and then changed his speed to 60 km/hr for the next 30 mins. Hence, total distance traveled by John will be the distance he covers in the entire 1 hour.

Time = 0.5 hr

Speed = 30 km/hr

Distance covered $= s p e e d \times t i m e = 30 \times 0.5 = 15 k m$

Now, new speed = 60 km/hr

Time = 0.5 hr

Distance covered $= s p e e d \times t i m e = 60 \times 0.5 = 30 k m$

Total distance covered by him = 15 + 30 = 45 km in one hour.

$A v e r a g e s p e e d = \frac{T o t a l d i s t a n c e t r a v e l l e d}{T o t a l t i m e}$
Average speed $= (\frac{45}{1}) \frac{k m}{h r}$
Average speed = 45 km/hr

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