Question

a car covers a distance of 80km at a certain speed . Had the speed been 12km/h , the time taken for the journey would have been 20 min less . Find the original speed of the car​

Answer 1

Answer:11.43km/h

Step-by-step explanation: Let original speed be ‘x’.

Then we know time, t= distance/ speed

 20 minutes =(20/60)hr

 t=80/12 = (80/x) - 20/60

   t=80/12 = (240-x)/3x

      Cross multiply

   t=80(3x)= 12(240-x)

   t=240x = 2880-12x

   t=240x+12x=2880

   t=252x=2880

   =>252x = 2880

              x= 2880 /252

              x=11.43(to 2 decimal point)

    x is original speed, therefore original speed is 11.43km/h.