HSTs (Half Square Triangles): a square that’s been cut in half once to make two right-angle triangles. A right-angle triangle has one 90-degree angle (think of an “L” shape) and two equal sides.
Making an HST is easy to do. Simply determine the finished size of the square needed and add 7/8” to it. An easy example: a 2” square is composed of two right-angle triangles that have been cut to 2-7/8”.
Test: You need to make a HST unit that is 2½” square. How large do you need to cut the right-angle triangles?
Skill Builder
Requirements: rotary cutter, self-healing mat, acrylic ruler, four scraps of fabric 3-3/8” square (two lights and two darks).
1. Cut each 3-3/8 square of fabric in half diagonally once.
2. Using a 1/4” seam, sew a light triangle to a dark triangle.
3. Press the seams toward the dark fabric.
4. Trim off the dog ears.
5. Arrange the HSTs in a pinwheel design.
6. Sew the pinwheel together.
Test: How big should the resulting square be?
Answers:
How large do you need to cut the right-angle triangles for a 2-1/2 square?
2-1/2 + 7/8
First, find the common denominator so you can add the numbers. To add fractions, both bottom numbers have to be the same, and it's always the (a) larger number. To convert 1/2 to a 1/8" number, divide the large number (8) by the small number (2) and put the result (4) over 8. So 2-4/8 + 7/8 = 2-11/8
Oops! Can't have a larger number on top in fractions... So divide the top number (11) by the bottom number (8) and you get the result 1-3/8. So 2-11/8 = 2 + 1-3/8 = 3-3/8.
How big should the resulting square be? 5-1/2”
Another Test: What are:
1/2 + 3/8
1/4 + 3/4
1/4 + 5/8
1/4 + 1/8
1/4 + 3/8
Answers:
1/2 + 3/8 = 7/8
1/4 + 3/4 = 1
1/4 + 5/8 = 7/8
1/4 + 1/8 = 3/8
1/4 + 3/8 = 5/8
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