How old is Ann?

#1

Post by ibobev » Thu, Jul 30, 2026, 12:14 PM UTC

How old is Ann?
quuxplusone.github.io

Re: How old is Ann?

#2

Post by nly » Thu, Jul 30, 2026, 1:25 PM UTC

Opus says Ann is 18

Re: How old is Ann?

#3

Post by bmfischer3 » Thu, Jul 30, 2026, 1:26 PM UTC

This has flashbacks to GMAT problems.

Re: How old is Ann?

#4

Post by gh5000 » Thu, Jul 30, 2026, 1:31 PM UTC

nly wrote: post #2

Opus says Ann is 18

and the circle remains unbroken

Re: How old is Ann?

#5

Post by tines » Thu, Jul 30, 2026, 1:41 PM UTC

Wait so how old is she?

Re: How old is Ann?

#6

Post by feelamee » Thu, Jul 30, 2026, 1:42 PM UTC

what the true answer? oh, there is no? My intuition says that Ann now is 24

Re: How old is Ann?

#7

Post by Cockbrand » Thu, Jul 30, 2026, 1:44 PM UTC

nly wrote: post #2

Opus says Ann is 18

Sounds about right.

How I understand it:

Mary is 24, Ann is a few (n) years younger

  M = 24
  A = M-n

Mary is twice as old as Ann was when Mary was as old as Ann is now. So we have to deduct the age difference twice from Mary's current age to find out how old Ann was when Mary was as old as Ann is now, which is half Mary's current age:

  M-2n = M/2 = 12

  M-2n = 12 --> n=6

So the age difference is 6, and Ann is 18.

Re: How old is Ann?

#8

Post by lordgrenville » Thu, Jul 30, 2026, 1:47 PM UTC

"Any eighth-grade boy or girl who is 'all there' should solve it in about thirty seconds" is hyperbole (it took me a couple of minutes), but in general the public reaction to this seems like a demonstration of the Flynn effect.

Re: How old is Ann?

#9

Post by judofyr » Thu, Jul 30, 2026, 1:51 PM UTC

Rephrasing it makes it easier to grasp:

Mary is 24 years old. When Mary was Ann’s current age, Ann was 12 years old (half Mary’s current age).

This makes it a bit easier to realize that Ann’s age has to be right in the middle of 12 and 24.

Re: How old is Ann?

#10

Post by saidnooneever » Thu, Jul 30, 2026, 1:51 PM UTC

tines wrote: post #5

Wait so how old is she?

well into the post-geriatric era by now