Multiple choice

A car travels first $30 km$ with a uniform speed of $60 kmph$ and then next $30 km$ with a uniform speed of $40 kmph$. Find the average speed of the car.

  1. $24\ kmph$
  2. $48\ kmph$
  3. $72\ kmph$
  4. $96\ kmph$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Average speed is total distance divided by total time. Total distance = 30 + 30 = 60 km. Total time = (30/60) + (30/40) = 0.5 + 0.75 = 1.25 hours. Average speed = 60 / 1.25 = 48 kmph.

AI explanation

When equal distances are traveled at two different speeds, the average speed is calculated using the harmonic mean formula: 2 times V1 times V2 divided by V1 plus V2. We plug in the uniform speeds of 60 kmph and 40 kmph for the two halves of the journey. This gives 2 times 60 times 40 divided by 60 plus 40, which equals 4800 divided by 100. The average speed of the car is 48 kmph.

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