Paul Dundon’s Weblog


A little cheese and a little whine

Intelligence Testing

It’s quite a long and involved tale that leads to my looking at but there I found the following puzzle:



Presumably, the creator of the puzzle expects us to reason as follows: The four symbols in the top row are the same, so each has a value of 28/4=7; the two bananas in the second row are therefore together worth 30 – 7*2 = 16 so each banana is worth 8. The last two rows are a little trickier but by applying this sort of reasoning one reaches the conclusion that the missing number is 25.

It was only later that I realised the symbols are completely irrelevant. The total of the rows must equal the total of the columns, so the missing number must be (28+30+20+16)-(19+20+30), a much easier calculation.

This leads me to wonder:

  1. Whether the puzzle’s creator intended to provide two solution methods
  2. How many people, like me, choose the dumb one
  3. How people’s performance would change if one manipulated the symbols in, say, the bottom two rows, to make the puzzle solvable only by the second method

Filed under: Psychology

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My Bookshelf

The Golden Bough
The Value of Nothing
The Fire
A Wolf at the Table
Devil Bones

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