This triangle is constructed from 10 coins.  What is the smallest number of coins that need to be moved to make the triangle point downwards?

As ever, please do NOT post your answers, but do say whether you think you have solved it and how long it took.  Solution on Monday.

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.

1. Bob O'H says:

Took me about 2 seconds. Assuming I’m right…

1. AMWhy says:

I didn’t even finish the question 😦 very old puzzle that I have seen many times before.

2. Murray P says:

Are they 5p or 10p pieces?

1. NoAstronomer says:

ROFL

3. Anonymous says:

Done – in about 20 seconds.

4. Done. But I think my answer is cheating kind of. about 10 seconds.

5. FoleyIsGood says:

Yep, 20-30 seconds.

6. vishal garg says:

Got one solution in 5s but another improved one in another 2-3 minutes.

7. cozdas says:

easy! 10 seconds

8. Sari1967 says:

Not too long today but only if I got the correct answer

9. Criticalbounce says:

10 seconds. Maybe too easy? I guess I’ll find out monday…

10. M says:

Instantly…

Hope i’m right.

11. chris r says:

got it,took a couple of seconds (hope i’m right)..

12. Yes, fairly easy (for a change).

13. Roland says:

Depending on how you read the question, 2 solutions in a few seconds 🙂

1. Savant says:

Read it again. The problem asks for the smallest number. That means that there is only one solution.

2. Roland says:

There is only one solution, however what that is depends on how you interpret Richards question…

14. lenasteapot says:

About 30 seconds. If I’m right. 🙂

15. Done in a couple of seconds (I think!)

16. rodney says:

about 5 sec assuming i am right. i think even two possibilities based on how its worded

17. Marion says:

Did this quickly but then I have seen it before.

18. Edgar says:

Well, I think I-ve done it, but there may be a better answer, I just haven-t found it.

Anyway, depending on how you look at it, the triangle could already be pointing downwards left or downwards right.

19. Andy says:

None, you just have to view it in an Australian frame of reference…

20. Berhard says:

but it already points downwarts.. in a rightish downwards direction and in leftish downward direction. …

If you want it to point straigth down, … also possible, 3 seconds..
without moving the upper and lower boundaries of the triangle an additional coin is required to be moved..

21. Robot says:

22. Berhard says:

sorry, have anohter (presumably incorrect solution).. after a few minutes.. definitivly including the minimum of coins to be moved…

23. Simon says:

See, I think I’ve done it and it was far too easy so no doubt on Monday the answer will be something like ‘π x happiness’

Oh how Mondays make me feel stupid.

24. Dan says:

That was too easy. 2 seconds.
If someone get’s less that that though, I’ll be *really* impressed

25. ANuRa says:

Done! Three seconds! (Although I had the feeling I had seen something similar somewhere…)

26. Got it wrong in about twenty seconds.
Got it right in a further twenty and made a 25% saving….

27. About 5 seconds, assuming I am right… I can’t find an alternative with fewer moves.

28. fcopplo says:

Solved this in 0.1237 seconds

29. mittfh says:

I’ve seen it before, so about 1/2 s after seeing the illustration.

30. Anonymous says:

I solved it yesterday

31. Bletherskite says:

About 30 secs to get one answer and then about another 45 secs to get a better one.

32. Two solutions in 10 seconds. Because the puzzle is old, or because I am.

33. Lazy T says:

Too easy, how about fewest moves to a dodecahedron? or a rabbit? or hyperlipoproteinurea?

34. The Russell Harty Commemoration Orchestra says:

it can be done in no moves- just walk around to the other side of the table

That’s exactly what I was going to say. 🙂

35. there is the obvious way and then the trick which we normally miss – i advise people to recount their moves before monday

36. Your link to the free puzzles is giving a Error 404 – Not Found page.. . .Hey, wait a minute. Is that the puzzle? I’m confused.

37. NoAstronomer says:

I too got a quick answer in a few seconds and then improved it with a minutes thought.

38. SeleneBlueSky7 says:

Done it. Half-a minute? I’m quite sure. 🙂

39. I see 2 possible answers. There is also an interpretive shade of grey in the possible answer.

40. Mark G says:

Really? That took a couple of seconds to work out.

41. Jerry says:

It took me about a minute to see the core pattern. I will check in on Monday to see if I got the correct answer.

42. Jon d says:

Very quickly, think I’ve seen it before tbh. (Nothing wrong with that though)

43. Rich says:

Isn’t it already pointing downwards? If you assume that one of the bottom corners of the triangle is the point. 5 seconds.

44. Emu says:

Depends on the exact rules. I found three different solutions, took me about 1 minute for all of them.

45. Mickey D says:

5 secs

46. SimonP says:

If you are able to see the shape not as a triangle, but a composite of two items (one which will remain unchanged) the answer jumps out at you.

47. spiderabc1 says:

Again I don’t think this has anything to do with maths, but I’m going to pretend and have a shot.

48. Mr. D says:

Ah. I got one answer in about 20 secs, but then spent another minute seeing if I could find a better one. I believe I have the right answer now. Can’t see a better solution

49. About 2/3 seconds. And looking into the future, I can see it’s right, so fairly confident…

50. Two answers – one involving three coins fewer than the other.

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