To show that they used the same amount of ribbon you could take the 1 yard and divided into different sized equal groups.
1 yard divided by four equals 1/4 yard for each of four ribbons.
1 yard divided by six equals 1/6 yard for each of six ribbons.
You could have ribbons the size of 1/4 our yard and 1/6 yard, but you would have different amounts of each.