Question

car moves with a speed of 30 km/h–1 for half an hour, 25 km/h–1 for one hour and 40 km/h–1 for two hours. Calculate the average speed of the car.

Answer 1

$\huge{\mathfrak{\underline{Answer:}}}$


34.28 km/hr

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$\huge{\mathfrak{\underline{Solution:}}}$

Distance covered in half an hour at 30 km/hr
= S × T
= 30 × $\dfrac{1}{2}$

= 15 km

Distance covered in one hour at 25 km/hr
= S × T
= 25 × 1
= 25 km

Distance covered in two hours at 40 km/hr
= S × T
= 40 × 2
= 80 km

Total Distance = 15 + 25 + 80
Total Distance = 120 km

Total Time = $\dfrac{1}{2}$ + 1 + 2

Total Time = $\dfrac{7}{2}$

Therefore, Average Speed
= $\sf \dfrac{Total \: Distance}{Total \: Time}$

= $\sf \dfrac{120 \times 2}{7}$

= $\blue {\boxed{\sf{34.28 km/hr}}}$

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Answer 2

speed = 30km/h

time = 1/2h

distance = 30 * 1/2 = 15km

speed = 25km/h

t = 1h

distance = 25 * 1 = 25km

speed = 40km/h

t = 2h

distance = 40 * 2 = 80km

total distance = 15 + 25 + 80 = 120km

total time = 3.5h

avg speed = 120/3.5 = 34.29km/h