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AB Crossed Floor Product (Posted on 2021-12-08) Difficulty: 3 of 5
Determine positive real numbers A and B that satisfy this equation:
2*A*floor(B) = 2020, and:
3*B*floor(A) = 2021

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Solution solution Comment 2 of 2 |
If I had known how easy (and early in the search) this was, I'd not have written the program.

The logic is to test the possible values of floor(A), as that's guaranteed integral; then from that find the exact value of B; then use floor(B) to find A. As soon as the final A agrees with the assumed floor(A), that's a solution.

clc
clearvars

syms a b fa fb
for fa=1:1200
   b=sym(2021)/(3*fa);
   fb=floor(b);
   a=2020/(2*fb);
   if floor(a)==fa
       disp([a b])
       disp([eval(a) eval(b)])
   end
end

produces

[1010/673, 2021/3]
          1.50074294205052          673.666666666667
          
indicating          

A = 1010/673 ~=  1.50074294205052 
B = 2021/3 ~=  673.666666666667

found on the very first try, of floor(A) (variable fa) equal to 1.

 

  Posted by Charlie on 2021-12-08 07:37:10
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