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4/5 x 1/2

Reason:

= 2/5 x 1/1

Compare numerators with denominators. 4 and 2 have greatest common factor = 2. Divide 4 by 2. Divide 2 by 2.

= 2/5

Multiply 2 by 1 to get the numerator. Multiply 5 by 1 to get the denominator.