Question 1208181: Solve the missing number
25 35 47
17 5 61
11 72 ?
Found 3 solutions by greenestamps, ikleyn, mccravyedwin:
Answer by greenestamps(13198)   (Show Source):
You can put this solution on YOUR website!
This is not a math problem; it is only a puzzle.
Arguments could be made for many different possible answers.
The only way to know the right answer is to ask the author of the puzzle what the right answer is.
Answer by ikleyn(52778)  (Show Source):
You can put this solution on YOUR website! .
If you have nothing to do, you may place "x" instead of the question mark,
equate the determinant of the matrix to zero and solve for x.
Or, alternatively, you may require the sum of elements of the matrix to be equal to zero.
Then you obtain another equation to determine the value of x.
Again, if you have nothing to do, you may entertain yourself doing it.
Third possible entertainment is to equate the trace of the matrix to zero (the sum of the diagonal elements)
and find x from this equation.
Fourth possibility is to place any number instead of x, for example,
73, -289,  , e,  ,  or  ,
since nothing in the problem prohibits you to do it.
Thus, if you really have nothing to do and struggle of it, you may have several ways to entertain yourself.
The only thing which I do not understand, is THIS: do you really think that at this forum I will entertain you ?
If you think so, you make very crude mistake: this forum is not for puzzles.
At this forum the tutors perform another job: we work to teach real students to real Math.
To come here for puzzles is the same as to come to a grocery store for hardware.
If you are seeking help for puzzles and want others entertain you and generally make
your job substituting yourself, find another web-site/forum in the Internet.
If you stop posting your puzzles to this forum, we, the tutors, will be infinitely happy.
Have a super-nice day.
Answer by mccravyedwin(406)  (Show Source):
You can put this solution on YOUR website!
We begin with the first row, by adding the first two numbers:
25+35=60 then we subtract 13. Why subtract 13? Because we
don't like unlucky numbers,
60-13=47.
For the second row, we switch to multiplication. Why switch
to multiplication? Because we like to alternate between addition
and multiplication. We like variety.
17x5=85. Then to determine what we subtract this time,
we add 1 to each digit of what we subtracted last time,
which was 13.
Adding 1 to each digit of 13, we get 24.
So we subtract 24 from 85 and get 61.
For the last row, we switch back to addition.
We add 11 and 72 and get 83.
Then to determine what we subtract this time,
we again add 1 to each digit of what we subtracted
last time, which was 24.
Adding 1 to each digit of 24, we get 35.
So we subtract 35 from 83 and get 48.
Answer: 48. Simple, huh?
Edwin
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