Amanda is making a small quilt that is 36 inches by 54 inches. She wants to add a 3 inch border of trim. She has 10 ft. of trim. How much more trim does she need?

The dimensions of the quilt after adding a 3 inch border of trim is:

(36+3) inches by (54+3) inches ==> 39 inches by 57 inches

The perimeter of the quilt with this 3 inch border trim addition is:

2(39 in) + 2(57 in) = 78 in + 114 in = 192 inches

Therefore, she needs a total of 192 inches of trim for the 3 inch border.

We are given that she has 10 ft of trim, we need to convert the total amount we found in inches into feet. Since there are 12 inches in one foot, then

(192 in)*(1 ft / 12 in) = 16 feet

Therefore, she needs a total 16 feet of trim for the 3 inch border she's adding on.

Since she already has 10 feet of trim, she will need 6 more feet of trim (16 ft - 10 ft = 6 ft).