Brain Teasers are Back!

Another “while” has passed so …

Number the balls 1 to 12 (simply for reference). Divide them into 3 Groups of 4

1st Weighing.

Compare Group 1,2,3,4 with Group 5,6,7,8

If Group 1,2,3,4 is heavier than Group 5,6,7,8 then IF the odd ball is in Group 1,2,3,4 it is heavy and IF the odd ball is in Group 5,6,7,8 it is light. Go to 2A

If Groups 1,2,3,4 and 5,6,7,8 do balance, the odd ball is in Group 9,10,11,12. Go to 2B

2nd Weighing

2A Compare Group 1,2,7,8 with Group 5,9,10,11

If Group 1,2,7,8 is heavy then either 1 or 2 is heavy or 5 is light. Go to 3A

If Group 1,2,7,8 is light then either 7 or 8 is light. Go to 3B

If Group 1,2,7,8 and Group 5,9,10,11 balance then 3,4 or 6 is the odd ball. Go to 3C

2B Compare Group 1,2,3 (in fact any 3 balls from 1 to 8) with Group 9,10,11.

If Group 9,10,11 is heavy then the odd ball is 9,10 or 11 and is heavy. Go to 3P

If Group 9,10,11 is light then the odd ball is 9,10 or 11 and is light. Go to 3Q

If Group 1,2,3 and Group 9,10,11 balance then the odd ball is 12. Go to 3R

3rd Weighing

3A Compare 1 and 2 and recall 5

If 1 is heavy then 1 = odd ball and is heavy

If 2 is heavy then 2 = odd ball and is heavy

If 1 and 2 balance then 5 is the odd ball and is light

3B Compare 7 and 8

If 7 is light then 7 = odd ball and is light

If 8 is light then 8 = odd ball and is light

3C Compare 3 and 4 and recall 6

If 3 is heavy then 3 = odd ball and is heavy

If 4 is heavy then 4 = odd ball and is heavy

If 3 and 4 balance then 6 is the odd ball and is light

3P Compare 9 and 10 and recall 11

If 9 is heavy then 9 = odd ball and is heavy

If 10 is heavy then 10 = odd ball and is heavy

If 9 and 10 balance then 11 is the odd ball and is heavy

3Q Compare 9 and 10 and recall 11

If 9 is light then 9 = odd ball and is light

If 10 is light then 10 = odd ball and is light

If 9 and 10 balance then 11 is the odd ball and is light

3R Compare 12 with any ball

If 12 is heavy it is the odd ball and is heavy

If 12 is light it is the odd ball and is light

I will try to post a diagram below which might help.

Perhaps not the greatest diagram, but it should help if you click on the “full screen” button and read it in conjunction with the text above.

Hi Don,

7 6 8
1 3 5
9 2 4

seems close, as only the last column is wrong (36 instead of 33). I’ll keep thinking, but perhaps my half- finished solution is motivation enough for someone else.

Thanks for giving it a go Mulberry.

So close, (as they say) yet so far away !!! (sorry)

The 8, 5 and 2 are in the right place.

The teasers that I posted today should be much more straightforward (I hope)

Thanks for the hint, it’s

9 4 8
2 1 5
6 2 7 then.

The 2 and 5 had to be true, but I got the 9 in the wrong spot in the first column. Everything went wrong from there.

Brilliant Mulberry, well done.

There is a slight “typo” in your result, (but that’s all). You’ve got it !

Aargh, 3 1 5 for the second row, of course. I should have posted a photo, but given my handwriting…

Yep, join the (bad handwriting) club !

Who is the most stupid ?

Hi FR,

There really isn’t sufficient information about the situation to arrive at any meaningful conclusion.

I appreciate that the publication from which the cartoon was abstracted states that No 1 is the most stupid. But both Beachcomber and IB in another thread have provided sufficient comment to call into question that conclusion.

Nice cartoon though !

1 Like

Missing Signs

Start in the bottom left corner with the number 9 and work clockwise to end up with 11.

First, use any combination of the four basic arithmetic signs ie “plus”; “minus”; “multiply” and “divide” to end up with 11. No need to use all of the signs, but each and every gap between the numbers needs a sign. The gap between 4 and 11 is already filled with the “Equals” sign.

Now try it again, but this time you must use each of the four basic signs at least once.

Missing Number

What number should replace the question mark ?

A 4 should fit in nicely.

A 4 is perfect !

Nicely done Mulberry.

Helping one of my grandsons improve his concentration and his arithmetic. So many kids these days have just never learned their times-tables and as a consequence become distracted when the have to pull their calculator out to do some trivial interim calculation.

So I created the following charts for him, which I scrounged from my school books from 65 years ago … (we actually created several charts to give him more practise)

We also created two Excel spread sheets to check the answers. But he was only allowed to put the
equation in the top-left cell in each spreadsheet and then “drag-to-copy” all the other cells.

Ok, none of it’s difficult, but you might like to print them out and give them a go !

Let me know how you got on !!

I think the right answer for the tree one is 4. He is the only one endangering himself.

Could be that . However he looks depressed, so more suicidal than really stupid.

Let’s face it, all four are stupid, assuming of course that we are looking at a tree with relevant branches 20 or 30 ft or so above hard ground.

But of course, that’s just the first of many assumptions.

As an alternative, let’s assume that there is a large airbag, as per the type in the Olympic high-jump, just out of shot beneath all four characters. The prize winner is the one who falls to the airbag first. Then No.3 would win the accolade of most stupid, since he will simply not win … unless he is in league with No.1 and/or No.2

Perhaps the saws are in plastic and will not cut the tree, perhaps there is a lake under them, perhaps airbag, perhaps the tree is artificial, in hard stone…
Or perhaps we should consider only what’s in the picture, thinking that they will die if fall down.