In a decimal 3 7/8

Remark.

1 / 2 = 0.5

1 / 4 = ( 1 / 2 ) / 2 = 0.5 / 2 = 0.25

1 / 8 = ( 1 / 4 ) / 2 = 0.25 / 2 = 0.125
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3 7/8 = 3 + 7 / 8 = 3 + 7 ∙ 0.125 = 3 + 0.875 = 3.875