Question

a car moves with a speed of 40 km/hr for 15 mins and then with a speed of 60 km/hr for the next 15 mins.find the total distance covered by the car

Answer 1

Distance = Speed × Time
= (v₁t₁ + v₂t₂)
= 2t(v₁ + v₂) ………[∵ t₁ = t₂ = t]
= 2 × 15 min × [40 kmph + 60 kmph]
= 30 min × 100 kmph
= 0.5 h × 100 kmph
= 50 km

Distance covered by car is 50 km

Answer 2

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Case (1)

Speed of the car = 40 km/h

Time taken = 15 min

$\dfrac{15}{60}$ = 0.25 h 

Distance of car $D_{1}$ = Speed × Time taken

40 × 0.25 = 10 km

Case (2)

Speed of the car = 60 km/h

Time taken = 15 min

$\dfrac{5}{60}$ = 0.25 h 

Distance covered by car $D_{2}$ = Speed × Time taken

60 × 0.25 = 15 km

Total distance covered [D] = $D_{1}\:+\:D_{2}$

 10 + 15 = 25 km

Therefore, the total distance covered by the car is $\textbf{25 km}$

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