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wu :: forums    riddles    easy (Moderators: Grimbal, ThudnBlunder, Icarus, william wu, towr, Eigenray, SMQ)    Expressing the number 77 using 1,2,3,4 « Previous topic | Next topic » Pages: 1  Reply Notify of replies Send Topic Print    Author  Topic: Expressing the number 77 using 1,2,3,4  (Read 501 times) Bill Cheong Guest Expressing the number 77 using 1,2,3,4   « on: Nov 9th, 2004, 3:02pm » Quote Modify Remove Express the number using the digits 1,2,3 and 4 by means of a formula that uses each digit exactly once. Any combination of elementary operations (including factorials) and decimal numbers are allowed. IP Logged Sir Col Uberpuzzler impudens simia et macrologus profundus fabulae     Gender: Posts: 1825 Re: Expressing the number 77 using 1,2,3,4   « Reply #1 on: Nov 9th, 2004, 3:40pm » Quote Modify Can I do 4*2/.1-3? IP Logged mathschallenge.net / projecteuler.net bob Guest Re: Expressing the number 77 using 1,2,3,4   « Reply #2 on: Nov 9th, 2004, 10:28pm » Quote Modify Remove (3+4)(2x4+3) IP Logged Barukh Uberpuzzler     Gender: Posts: 2276 Re: Expressing the number 77 using 1,2,3,4   « Reply #3 on: Nov 10th, 2004, 12:00am » Quote Modify bob, it seems you are using the digit '4' twice.   Couple of other examples:   [smiley=square.gif] (31 - .2)/.4 3!^2 + 41 [smiley=square.gif] IP Logged Barukh Uberpuzzler     Gender: Posts: 2276 Re: Expressing the number 77 using 1,2,3,4   « Reply #4 on: Nov 10th, 2004, 1:54am » Quote Modify How about expressing 94, 95, 97 using the same digits? This time, factorial is not allowed! IP Logged Fresno_Bob Newbie     Gender: Posts: 13 Re: Expressing the number 77 using 1,2,3,4   « Reply #5 on: Nov 10th, 2004, 6:51am » Quote Modify Well, pretty close...   4^(3.1+.2) ~ 97.00586   Can I clip it with the floor function? Then 94 = floor(3.1^4+2) 95 = ceil(3.1^4+2) 97 = floor(4^(3.1+.2)) IP Logged Sir Col Uberpuzzler impudens simia et macrologus profundus fabulae     Gender: Posts: 1825 Re: Expressing the number 77 using 1,2,3,4   « Reply #6 on: Nov 10th, 2004, 4:38pm » Quote Modify If the rounding functions are not allowed, I've found 94 and 97 using more elementary operations and 95 by a more questionable approach...   :: 94=32/.1+4 95=2*atan(1)+sqrt(4)+3 97=(sqrt(4)/.2-.3)/.1   And if atan is allowed, then we could use asin(1) as a building block for 90, which seems a little cheeky. :: « Last Edit: Nov 10th, 2004, 4:56pm by Sir Col » IP Logged mathschallenge.net / projecteuler.net TenaliRaman Uberpuzzler I am no special. I am only passionately curious.     Gender: Posts: 1001 Re: Expressing the number 77 using 1,2,3,4   « Reply #7 on: Nov 10th, 2004, 8:14pm » Quote Modify ::90 = 12*3/.4:: IP Logged Self discovery comes when a man measures himself against an obstacle - Antoine de Saint Exupery Barukh Uberpuzzler     Gender: Posts: 2276 Re: Expressing the number 77 using 1,2,3,4   « Reply #8 on: Nov 10th, 2004, 11:19pm » Quote Modify on Nov 10th, 2004, 6:51am, Fresno_Bob wrote: Can I clip it with the floor function? No.   on Nov 10th, 2004, 4:38pm, Sir Col wrote: And if atan is allowed It is not allowed.   Also, can you make 97 without using square root?   IP Logged Barukh Uberpuzzler     Gender: Posts: 2276 Re: Expressing the number 77 using 1,2,3,4   « Reply #9 on: Nov 19th, 2004, 1:50am » Quote Modify Is this thread out of interest? Anyway, here's an answer to my last question to Sir Col:   [smiley=blacksquare.gif]97 = .1 ^ (2-4) - 3[smiley=blacksquare.gif] « Last Edit: Nov 19th, 2004, 1:51am by Barukh » IP Logged Pages: 1  Reply Notify of replies Send Topic Print Forum Jump: ----------------------------- riddles -----------------------------=> easy   - medium   - hard   - what am i   - what happened   - microsoft   - cs   - putnam exam (pure math)   - suggestions, help, and FAQ   - general problem-solving / chatting / whatever ----------------------------- general -----------------------------  - guestbook   - truth   - complex analysis   - wanted   - psychology   - chinese « Previous topic | Next topic »

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