How to enter this program?

Question

Colton 2014-10-25

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评论： per isakson 2014-10-26

Hello, I have tried unsuccessfully for a couple hours to enter a program that loops until a number that is even, divisible by both 13 and 16, and whose square root is greater than 120 is found. I have reached a wall, so I have come to ask for help. Would using a while statement be the first step? Please don't solve this problem, I only ask for help getting it going. Yes, this is basic stuff, but I still have little understanding on it.

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Answer 1

Roger Stafford 2014-10-25

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You need to translate each of those conditions into a matlab logical proposition. For example if n is an integer you are investigating, try dividing it by 13, then comparing the 'round' of the quotient with the original quotient to see if it is still an integer after the division. And yes, the 'while' function is the right thing to use here. Keep it looping until all the conditions turn out to be true for the same integer, for which you can make great use of the "&" operation.

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Rick Rosson 2014-10-25

Try using || instead of &&.

Colton 2014-10-26

@Rick, thank you. That fixed my issues and I was able to find the correct value! And thanks everyone else for the help!

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Answer 2

Rick Rosson 2014-10-25

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编辑：Rick Rosson 2014-10-25

在 MATLAB Online 中打开

Here is a faster and simpler approach:

   a = 0;
   while a < 120^2
        a = a + 13*16;
   end

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per isakson 2014-10-26

Note &nbsp "square root is greater than 120"

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Answer 3

per isakson 2014-10-26

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编辑：per isakson 2014-10-26

在 MATLAB Online 中打开

Try

    >> factor( cssm )
    ans =
         2     2     2     2     2     5     7    13

where cssm is

    function ix = cssm()
        % chose a start value, which is larger than 120^2 and divisible by 16
        ix = 120*120+16; 
        while  ne( mod(ix,13), 0 )
            ix = ix + 16;
        end
    end