   SEARCH HOME Math Central Quandaries & Queries  Question from venkatesh, a student: A car travels a distance of 840 miles at a uniform speed if the speed of the car is increased 10 m/h more ,it takes two hours less to cover the same distance ,the original speed of the car was? options:75 m/h,65 m/h,60 m/h,55 m/h,45 m/h . can u explain it clearly ..pls A car travels a distance of 840 miles at a uniform speed.

First equation: Speed = 840/Time

If the speed of the car is increased 10 m/h more, it takes two hours less to cover the same distance,

Second equation: (Speed + 10) = 840/(Time - 2)

the original speed of the car was?

So now you have two equations and two unknowns, and you have probably learned how to solve this system.

options:75 m/h,65 m/h,60 m/h,55 m/h,45 m/h.

This gives you a second way to solve it: Put each Speed option in the first equation, which gives you a corresponding Time option. Put this Speed in Time in the second equation, to see if it balances.
If not, it is the wrong Speed.

Claude     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.