Gransnet forums

Chat

Four Fours

(120 Posts)
crun Thu 12-Mar-15 12:29:07

I thought I'd try you with a puzzle that our maths teacher Mr Garlick set us forty odd years ago, and see if it captures your interest or falls flat.

The idea is to write a formula for every integer between one and a hundred in terms of four fours. You can use as many mathematical symbols as you like, but the only numeral allowed is four, and you must use four of them, no more, no less. (As there's no correct character on the keyboard, use .4' for point four recurring.)

I'll start off with a few so you see the idea:

1= 44/44
2= 4/4+4/4
3= 4/4+4/sqrt(4)
4= 4/sqrt(4)+4/sqrt(4)

Let's do them in order, so that people don't cherry-pick all the easy ones first:

5= ???

soontobe Thu 12-Mar-15 12:58:18

5 = sqrt 4x4 + 4/4

soontobe Thu 12-Mar-15 12:58:46

That took me 15 minutes of my life!

crun Thu 12-Mar-15 13:10:32

[pedant]
Strictly speaking:

5= sqrt(4*4)+4/4

[/pedant]

6= 4!/4*4/4

soontobe Thu 12-Mar-15 13:12:36

I dont understand what you have written.
If you go pedantic on me, I have no hope.

Anya Thu 12-Mar-15 13:31:39

But you did solve it S2B just crun being a pedant as he says.

MiniMouse Thu 12-Mar-15 13:31:47

I'm with you Soon! confused

JoyBloggs Thu 12-Mar-15 13:37:26

crun Sorry if this is a daft question, but in your answer to '5' does * stand for the multiply symbol? (Or maybe a prob with my screen confused)

jinglbellsfrocks Thu 12-Mar-15 13:55:23

Crikey soon! That was amazing!

#haventacluewhathesonabout

Charleygirl Thu 12-Mar-15 14:08:43

Beyond my pea brain

KatyK Thu 12-Mar-15 14:15:12

I have no idea what that post means confused

soontobe Thu 12-Mar-15 14:34:58

7 = 4 + 4 - 4/4

I didnt understand your ! in the 6 one crun
nor the * which I too assume is x?

soontobe Thu 12-Mar-15 14:36:41

KatyK.

You have to try and make each number, but can only use the number 4, 4 times to try and achieve it.

jinglbellsfrocks Thu 12-Mar-15 14:38:44

What is the sqrt thing? Please tell me it's not 'squared'. I can't do squared stuff.

pompa Thu 12-Mar-15 14:44:41

7 = 4 + 4/4+4/4+4/4

pompa Thu 12-Mar-15 14:45:43

OK forget that, just read rules

pompa Thu 12-Mar-15 14:48:31

7=4+4-(4/4)

Pedants, I know the () are unnecessary but it makes it clearer

MiniMouse Thu 12-Mar-15 14:56:46

It's the ! In the 6 one that I don't understand either!

pompa Thu 12-Mar-15 15:02:58

! means factorial

n! means the product 1 × 2 × ... × n.4! = 1\times2\times3\times4 = 24

crun Thu 12-Mar-15 15:03:45

sqrt = square root

* = multiplication, I'm just in the habit of using computer terminology because I'm typing on a computer.

4! = four factorial = 4*3*2*1 = 24

next:

8= 4+4+4-4

Re pedantry:

5= sqrt(4*4)+4/4

but if you take away the brackets:

9= sqrt4*4+4/4

10= ???

KatyK Thu 12-Mar-15 15:09:56

Oh I see (or do I?) smile It's a long time since I was at school and I was rubbish at this sort of thing anyway,

soontobe Thu 12-Mar-15 15:33:03

I dont understand your 9 either!

10 = 4 + 4 + 4 - sqrt4

loopylou Thu 12-Mar-15 15:58:09

confused
Beyond me (today anyway)

petra Thu 12-Mar-15 16:02:39

This reminds me tooooo much of the maths teacher who hit me round the head so hard that my glasses went flying. That was in the last year of juniors and my maths stopped then.
So I won't read any further.

PRINTMISS Thu 12-Mar-15 16:10:14

I am just going to lie down!