Question 1164099
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Add 100 cm = 1 meter  to each 5m, 4m, 3m  and notice that


    (5+1)*(4+1)*(3+1) = 6*5*3 = 2*(5*4*3).


<U>ANSWER</U>.  The increase is 100 cm, or 1 meter.
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Nice entertainment problem (!)