The total length cut from the 51-meter ribbon is 100 x 15 centimeters = <<100*15=1500>>1500 centimeters.
Since 1 meter is equal to 100 centimeters, then 1500 centimeters is equal to 1500/100 = <<1500/100=15>>15 meters.
Therefore, 51 - 15 = <<51-15=36>>36 meters of ribbon remains.
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