What Ages Solve the Postmen's Riddle?

  • Context: High School 
  • Thread starter Thread starter Evo
  • Start date Start date
Click For Summary
SUMMARY

The ages of the three sons of Postman B are 2, 5, and 9 years old, with the postman being 90 years old. The solution is derived from the clues given: the product of the ages equals the postman's age (90), and the sum of the ages equals the number of windows in a nearby building (16). The critical clue that resolves ambiguity is the existence of a middle child, which eliminates the possibility of twins, leading to the unique solution.

PREREQUISITES
  • Understanding of basic arithmetic operations: addition and multiplication.
  • Familiarity with the concept of prime numbers and factorization.
  • Knowledge of logical reasoning and deduction techniques.
  • Ability to analyze and interpret mathematical puzzles.
NEXT STEPS
  • Explore mathematical puzzles involving age problems and logical deductions.
  • Study prime factorization techniques and their applications in problem-solving.
  • Learn about combinatorial mathematics and permutations related to age problems.
  • Investigate similar riddles that require critical thinking and elimination of possibilities.
USEFUL FOR

This discussion is beneficial for puzzle enthusiasts, educators teaching logical reasoning, and anyone interested in mathematical problem-solving techniques.

  • #31
Be happy it wasn't "My youngest son has red hair"

Then the choices would be:
36:
2,2,9
1,6,6

40:
2,2,10
1,5,8

or

90:
3,3,10
2,5,9
 
Mathematics news on Phys.org
  • #32
why couldn't you have 2 children of the same age who weren't twins? they could b 3, 3, 10 with one of the 3 year olds being older than the other. even if they are twins, one of them would still be older, and therefore the middle child.
 
  • #33
Unless the postman worked in Utah, this would be highly unlikely. I'll let the biology folks tell us the least time between successive births (I know there are several factors involved, including how long you breast-feed)...but I'm sure that 2 births from one woman, less than a year apart is virtually unheard of.

Or he could always divorce a pregnant wife; re-marry and make his new wife pregnant in short order...

Or there could be illegitimate children...

Clearly, we're nitpicking and getting beyond the intended realm of the puzzle.
 
  • #34
You really tripped them up with this one.
 
  • #35
I don't know how rare it is, but I'm 10 months older than my younger brother.
 
  • #36
Brennen said:
why couldn't you have 2 children of the same age who weren't twins? they could b 3, 3, 10 with one of the 3 year olds being older than the other. even if they are twins, one of them would still be older, and therefore the middle child.

Well, while you're at it, why don't we allow non-integer ages. That way there's an infinite number of possible combinations.

In practice, there is almost always an older twin and a younger twin, since they don't come out at the same time, but a few minutes apart.
 
  • #37
I grew up with 2 kids that are 11 1/2 months apart.
 
Last edited:
  • #38
not to mention that a 90 year old man probably wouldn't have kids that younge.
Great problem though
 
  • #39
NateTG said:
Be happy it wasn't "My youngest son has red hair"

Then the choices would be:
36:
2,2,9
1,6,6

40:
2,2,10
1,5,8

or

90:
3,3,10
2,5,9

Speaking of a postman who's 36, is it not also possible that the children are 1, 3, and 9? This still satisfies all the requirements of the original problem, it seems to me.
 
  • #40
Adelaine said:
Speaking of a postman who's 36, is it not also possible that the children are 1, 3, and 9?
1*3*9=27 :biggrin:
 
  • #41
For anyone interested, I ran a script on all the possible solutions for this problem assuming that:

1) the product is <= 1000
2) the numbers ("ages" in this case) are positive, whole numbers

Solutions assuming there's a "middle child":
1,5,8
2,5,9
3,6,8
1,13,18
1,12,21
1,11,27
2,10,16
5,8,9
2,9,24
3,10,15
1,10,45
3,8,27
3,9,25
6,8,15
4,10,18
1,25,32
1,24,34
2,17,25
1,22,40
5,9,20
2,9,50

If the problem specified "youngest child", you would get:
1,6,6
1,5,8
2,6,6
2,5,9
3,6,8
1,15,15
1,13,18
1,12,21
2,12,12
1,11,27
2,10,16
5,8,9
2,9,24
3,10,15
1,10,45
4,12,12
3,9,25
4,10,18
1,28,28
2,20,20
1,25,32
1,24,34
2,17,25
1,22,40
3,18,18

"Oldest child":
2,2,9
3,3,8
3,3,25
4,4,18
6,6,16
3,8,27
6,8,15
4,4,49
5,5,32
5,9,20
2,9,50
6,6,27

DaveE
 
  • #42
Evo said:
If you really wanted to be fussy, since a house cannot have a fraction of a window, it also means that the ages of the sons must all be in integers (whole numbers) and not involve fractional ages.

What if more than one of them has a fractional age?

This part is just stupid
 

Similar threads

  • · Replies 20 ·
Replies
20
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
1K
  • · Replies 10 ·
Replies
10
Views
2K
Replies
24
Views
4K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 7 ·
Replies
7
Views
9K
  • · Replies 6 ·
Replies
6
Views
8K
  • · Replies 26 ·
Replies
26
Views
3K