perplexus.info :: Probability : Mountain Motif

Mountain Motif (Posted on 2010-04-07)

A five digit positive integer is a mountain number if the first three digits are in strictly ascending order and the last three digits are in strictly descending order. For example, 46872 is a mountain number, but none of 43434, 54456 and 46766 is a mountain number.

Determine the probability that N is a mountain number, given that N is a positive integer chosen at random between 40000 and 99999 inclusively.

Submitted by K Sengupta

Rating: 3.5000 (2 votes)

Solution: (Hide)

The required probability is 0.0101.
For an explanation, refer to the solution submitted by Charlie in this location.
You can also refer to the methodology posited by Ady TZIDON in the comments section.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Solution (using Excel)	hoodat	2010-04-20 00:37:30
A mountain RANGE?	ed bottemiller	2010-04-08 17:18:56
Let's generalize- no middle point needed	Ady TZIDON	2010-04-08 14:02:58
re(2): my way	Ady TZIDON	2010-04-08 13:05:31
re: my way	Charlie	2010-04-08 12:10:06
my way	Ady TZIDON	2010-04-08 10:09:52
solution	Charlie	2010-04-07 11:44:17
six of one, half-dozen of another	ed bottemiller	2010-04-07 11:40:37

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