Yashvi rides a bicycle at a uniform speed. If the speed had been 4 km/hr more, it would have taken 1 hourless to travel 48 km distance. Determine her speed.

  12 km/h

Explanation:

Let v represent Yashvi's speed in km/h.

  time = distance/speed

  48/v -1 = 48/(v+4) . . . . time is 1 hour less at v+4 km/h

  48(v+4) -(v)(v+4) = 48v . . . . . multiply by v(v+4)

  48v +192 -v^2 -4v = 48v . . . eliminate parentheses

  v^2 +4v -192 = 0 . . . . . . . . . . put in standard form

  (v -12)(v +16) = 0 . . . . . . . . . . factor

  v = 12

Yashvi's speed is 12 km/hour.

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Check

At 12 kph, it takes 48/12 = 4 hours to ride 48 km. At 12+4 = 16 kph, it takes 48/16 = 3 hours to ride 48 km. That's 1 hour less, as it should be

pe = weightxheight = 2000x1000=2,000,000joules

reserve is the answer