perplexus.info :: General : Keeps on ticking...

Keeps on ticking... (Posted on 2003-08-01)

Two friends, Joe and Moe, were born in May, one in 1932, the other a year later. Each had an antique grandfather clock of which he was extremely proud. Both of the clocks worked fairly well considering their age, but one clock gained ten seconds per hour while the other one lost ten seconds per hour.

On a day in January, the two friends set both clocks correctly at 12:00 noon.
"Do you realize," asked Joe, "that the next time both of our clocks will show exactly the same time will be on your 47th birthday?"
Moe agreed.

Who is older, Joe or Moe?

Submitted by DJ

Rating: 4.3571 (14 votes)

Solution: (Hide)

Moe.

To find the answer, we have to find how long it will be before the clocks show the same time again. This is when the slow clock loses six hours, and the fast one gains six hours.
This will take 90 days, at which point they will come together at 6:00.

On a calendar, there are 90 days between noon January 31, and noon May 1 in years with no leap year.
Therefore, Moe's birthday must be May 1, they are setting the clocks together on January 31, and Moe's 47th birthday must not fall in a leap year.

One of the men was born in 1932 (the elder); the other in 1933.
If Moe had been born in 1933, his 47th birthday would have been in 1980, a leap year.
This means that Moe must be older, born in 1932, and the time of this problem is 1979. Joe will celebrate his 47th birthday in May 1980.

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

Subject	Author	Date
answer	K Sengupta	2007-11-14 04:01:44
maybe itz...	dorkdork	2003-08-02 22:27:35
Tricky ...	Bryan	2003-08-01 10:24:26
No Subject	Brian Wainscott	2003-08-01 10:18:03

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