Multiple choice

Some part of a journey of $555$ km was completed by a car with speed $60$ km/h. Then the speed is increased by $15$ km/h and the journey is completed. If it takes $8$ hours to reach, find the time taken and distance covered by $60$ km/h speed.

  1. $2$ hours, $90$ km.
  2. $3$ hours, $180$ km.
  3. $4$ hours, $270$ km.
  4. $5$ hours, $90$ km.
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B Correct answer
Explanation

Let t be the time at 60 km/h. Distance = 60t + 75(8-t) = 555. 60t + 600 - 75t = 555. -15t = -45, so t = 3 hours. Distance at 60 km/h is 60 * 3 = 180 km.

AI explanation

Let the distance covered at 60 km/h be x. Using the formula Time equals Distance divided by Speed, the total time is x/60 plus the remainder (555 minus x) divided by 75, which equals 8 hours. Multiplying the entire equation by 300 gives 5x plus 4 times (555 minus x), equaling 2400, which simplifies to x plus 2220 equals 2400. Solving for x gives a distance of 180 km, and the time taken is 180 divided by 60, which equals 3 hours.

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