<PRE><B>Question 297621</B>
A perfect square is an integer that is the result of the squaring of another integer.


25 would be a perfect square because it is the result of 5*5


169 would be a perfect square because it is the result of 13*13


the factors of the perfect square can be positive or negative.


Example


5*5 = 25


(-5)*(-5) = 25


Both 5 and -5 are square roots of the perfect square of 25.


In your problem:


square root of (2*40) = square root of 80 = 8.94427191 (not an integer)


square root of (5*40) = square root of 200 = 14.14213562 (not an integer)


square root of (20*40) = square root of 800 = 28.28427125 (not an integer)


square root of (40*40) = square root of 1600 = 40 (this is the perfect square)


Answer is selection D.






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