NumericalModerate2 marks
8(iii)
Mr. and Mrs. Das were traveling by car from Delhi to Kasauli for a holiday. Distance between Delhi and Kasauli is approximately 350 km (via NH 152D). Due to heavy rain they had to slow down. The average speed of the car was reduced by 20 km/hr and time of the journey increased by 2 hours. Find:
the original speed of the car.
Topic: Quadratic word problems
Previous-year question practice database
Answer
Exam answer
Original speed = 70 km/h.
Explanation
Let original speed x. 350/(x−20) − 350/x = 2. Solve x²−20x−3500=0 ⇒ x=70 km/h.
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