Question

28. A car covers a distance of 840 km at a constant speed.
If the speed of the car would have been 10 km/h less,
then it would have taken 2 hours more to cover the
same distance. What is the actual speed of the car?
यदि एक कार की चाल 10 किमी/घण्टे कम होती तो 840
किमी की दूरी तय करने में 2 घण्टे अधिक लगते, कार की
वास्तविक चाल ज्ञात कीजिए-
(a) 60 kmph
( (b) 70 kmph
(c) 80 kmph
( (d) 90 kmph​

Answer 1

Answer:

Let the original speed be x km/hr.

Then, [ 840/x - 840/( x + 10) ] = 2

⇒ 840 (x + 10) - 840x = 2x (x+10)

⇒ x2 + 10x - 4200 = 0

⇒ (x + 70) (x - 60 ) = 0

∴ x = 60 km/hr.