## September 16, 2011

### What is the speed of the car ?

A person drives with constant speed and after some time he sees a
milestone with 2 digits. Then travels for 1 hour and sees the same 2
digits in reverse order. 1 hour later he sees that the milestone
has the same 2 digits with a 0 between them. What is the speed of
the car?

Deepak said...

Car Speed was 45mph

1st Mile stone with 16
2nd with 61
and the final with 106

Babu vincent said...

speed of the car 45.

hotmail.com said...

Speed of the car 90.1st milestone 12, 2nd milestone 21 and 3rd milestone 102.

Occum said...

I say 45 mph. and he is travelling East to West. Mile markers are 1 mi. apart in Western States (Cal. excepted). Ideally the road would be flat like Kn or NE.. He hits mile marker 61 and travels one hr. to mi. marker 16. The difference is 45.

Secret SquÃ¯rrel said...

Deepak and Babu vincent are correct.

@hotmail.com - that's a bizarre answer. We're told that the car is travelling at a constant speed and takes 1 hour between each milestone.

Plus, 102 - 21 = 81 not 90.

@Occum - you're just making stuff up. Why on earth would you assume that the car is driving in the USA?

And you've got the direction wrong too. The car must pass the 16 mile marker first since we're told that the third marker has three digits.

Anonymous said...

Can anyone explain how one solutions this problem? Basic algebra? If so, what is the equation?
Thanks

soumyabrat said...

answer is 45 kmph .1st marker show 16 then 2nd show 61 and 3rd show 106

distance formula calculator said...

Speed of the car is 45kmph. First milestone will be done in 16 second one in 61 and the last one is 106.

Anonymous said...

speed=10B+A-(10A+B);
100A+B=10B+A+speed*1=2*10B+A)-(10A+B)
or
108A=18B or 6A=B, or A=1, B=6.
speed=61-16=45.

Anonymous said...

The problem should indicate that the final milestone's digits are not in the same order...it appears as if they are in the same order as the second marker, which doesn't allow for a solution. Thanks :)

Anonymous said...

The solution is pretty easy - if we label the digits of the first marker as "ab", then the mile markers are:

ab
ba
a0b

In that order. Since the same distance is traveled between each pair of markers, and since ba-ab < 100, we know that a must be 1. So the markers are:

1b
b1
10b

Now - since b + 2n ends in b, we know that n must end in 0 or 5, and b must be 1 or 6. The answer is 16, 61, 106, and the speed is 45 mph. -Kevin