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Age Disparities (Posted on 2021-12-06) Difficulty: 3 of 5
Four young people each made two statements about their ages:

  • Parker: I'm 18 years old. Remy is 15.
  • Quinn: I'm 13. Skyler is 17.
  • Remy: Parker is 16. Quinn is 12.
  • Skyler. Remy is four years younger than Parker.
    I'm three years older than Remy.

Only one of the four was a knight and made two true statements. The rest, knaves, alternated telling the truth and lying, though we don't know what phase they were in at the beginning.

What were their correct ages?


From Mensa Puzzle Calendar 2021 by Fraser Simpson, Workman Publishing, New York. Puzzle for November 9.

  Submitted by Charlie    
Rating: 4.0000 (1 votes)
Solution: (Hide)
If Parker were the knight, he'd be 18, Remy would be 15, Quinn 12 and Skyler 17, and both of Skyler's statements would be false, contradicting the fact that no complete liar was making any statements.

If Quinn were the knight, he'd be 13 and Skyler 17. Parker would be 16 and Remy 15, again making both of Skyler's statements false.

If Remy were the knight, Parker would be 16 and Quinn 12. Skyler would be 17 and Remy 15, still making both of Skyler's statements false.

So Skyler must be the knight.

With Parker at 18, Remy is 14 by Skyler's first statement and Skyler himself is 17. Quinn is 12 per Remy's true statement.

Other ages for Parker don't work out.

Alternatively,

clearvars, clc

for p=5:25
    for q=5:25
        for r=5:25
            for s=5:25
                ps=[p==18 r==15];
                if ps(1) || ps(2)
                qs=[q==13 s==17];
                if qs(1) || qs(2)
                rs=[p==16 q==12];
                if rs(1) || rs(2)
                ss=[p-r==4 s-r==3];
                if ss(1) || ss(2)
                    disp([p q r s])
                    disp(ps)
                    disp(qs)
                    disp(rs)
                    disp(ss)
                    disp(' ')
                end
                end
                end
                end
            end
        end
    end
end

assigns all possible sets of ages with each person being between 5 and 25, listing the truth values of all 8 statements, when each person's pair includes at least one true statement. The only three possibilities are:

    16    13    15    18
   0   1
   1   0
   1   0
   0   1

    18    12    14    17
   1   0
   0   1
   0   1
   1   1

    19    12    15    17
   0   1
   0   1
   0   1
   1   0

where 1 symbolizes true, and 0 false.

Indeed only ages 18, 12, 14 and 17 for Parker, Quinn, Remy and Skyler result in one of the people having two true statements.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
Puzzle ThoughtsK Sengupta2024-04-28 21:51:41
No Subjectsamytyu2024-04-27 22:22:39
No Subjectalijen2022-11-24 00:30:51
solnSteven Lord2021-12-06 13:22:16
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