The classic 4 4's challenge was first sent to us by SUNNY from SLOVENIA and we think it's the most extraordinary problem we've ever been sent! The question is simple enough:
The Rules:
Here are few answers with how they work out to give you the idea:
1 = 44/44
2 = 4/4 + 4/4 = 1 + 1
6 = (4+4)/4 + 4 = 8/4 + 4 = 2 + 4
12 = 4 x 4 - SQRT4 x SQRT4 = 16 - 2x2 =16 - 4
25 = (SQRT4 + SQRT4)! + 4/4 = (2 +2)! +1 = 4! +1 = 24 +1
55 = ((4!!)!! + 4!)/ 4!! + 4 = (8!!+24)/8 +4 = (384 +24)/8 +4 = 408/8 +4 = 51 +4
75 = ((4!)^SQRT4 + 4!)/ 4!! = (24^2 + 24)/8 = (576 +24)/8 = 600/8
Let us know how you get on! A lot of numbers have more than one solution, but if you get stuck, Sunny gave us the ANSWERS And now... the TOUGH version!
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TRIPLE FACTORIAL !!!
Take your number and subtract 3, then subtract 3 again and keep subtracting 3 until you get to 0 or less. Then multiply all the answers together to get the triple factorial. Therefore:
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INT (or the INTEGER function)If you get a number with a decimal after it, just ignore the decimal bit.
Therefore:
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131 = (((4!!)!! + 4!)/4!!) + (4!!)!!!
       = (((4x2)!! + 4x3x2x1)/(4x2)) + (4x2)!!!
       = ((8!! + 24)/8) + 8!!!
       = ((8x6x4x2 + 24)/8) + 8x5x2
       = ((384 + 24)/8) + 80
       = (408/8) + 80
       = 51 + 80
       = 131
155 = INT(SQRT((4!!)!)) - INT(SQRT((4!!)!!)) -4! -SQRT4
       = INT(SQRT((4x2)!)) - INT(SQRT((4x2)!!)) - 4x3x2x1 - 2
       = INT(SQRT(8!)) - INT(SQRT(8!!)) - 24 - 2
       = INT(SQRT(8x7x6x5x4x3x2x1)) - INT(SQRT(8x6x4x2)) - 26
       = INT(SQRT(40320)) - INT(SQRT(384)) - 26
       = INT(200.798) - INT(19.596) - 26
       = 200 - 19 - 26
       = 155
Admittedly they're not pretty, useful or even interesting, but you simply have to sit back and admire the sheer determination and brain power that produced the 101-200 answers!