perplexus.info :: Just Math : 2 + 2 = 5

2 + 2 = 5 (Posted on 2008-09-16)

Using only two 2s and any of the standard mathematical symbols, write an expression whose value is equal to 5.

An approach could be: sqrt((2 * 2)!) = 4.90

Standard mathematical symbols (for this problem) are: addition, subtraction, multiplication, division, exponentiation, square root, factorization, parenthesis, positive, negative, ln, log. Superfactorials and such are not excluded, but not part of the desired solution. Any symbol having a value of its own, such as e, pi, and infinity, is not authorized.

See The Solution Submitted by Leming

Rating: 4.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)

A simple modification -- trivial solution

| Comment 1 of 7

The ceiling function is the smallest integer greater than or equal to its argument. So

ceil(sqrt((2*2)!)) would work.

Placed into terms of the the floor, or integer, function of greatest integer smaller than or equal to its argument, that same variation is given as

-[-√((2*2)!)]

where the square brackets indicate the floor function.

Posted by Charlie on 2008-09-16 10:48:11

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