The fractions 1/4, 2/8, 3/12, 4/16, and 5/20 are equal in value because multiplying or dividing both a fraction's numerator and a fraction's denominator by the same value (i.e., 1 in this case since 2/2 = 1, 3/3 = 1, 4/4 = 1, etc.) does not change the value of the fraction.
