All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars
 perplexus dot info

 Formula None Racer (Posted on 2003-10-03)
A car is travelling at a uniform speed.
The driver sees a milestone showing a 2-digit number. After travelling for an hour the driver sees another milestone with the same digits in reverse order. After another hour the driver sees another milestone containing the same two digits as in the first one but the two digits separated by a zero(0).

What is the speed of the car?

 See The Solution Submitted by Ravi Raja Rating: 2.6000 (10 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
 Puzzle Solution (Method I) | Comment 33 of 35 |

Let the respective values in the three milestones be 10A+B, 10B+A and 100A+ B.

Since the driver drove the car at a constant speed, we must have:

(10B+A) - (10A+B) = (100A +B) - (10B+A)
or, 100A+B + 10A+B = 2(10B+A)
or, 110A+2B = 20B+2A
or, 108A = 18B
or, 6A = B

Since 10A+B is a two digit number, we must have A>=1. If A>=2, then B>=6*2=12>10, which
is a contradiction. This A =1, giving B=6

So the respective values in the three milestones were 16, 61 and 106. Accordingly, the car covered 61-16= 45 miles in one hour, so that  the required speed of the car is 45 miles per hour.

 Posted by K Sengupta on 2008-02-14 13:48:33

 Search: Search body:
Forums (0)