Parallel lines, quadrilaterals and triangles · Usually met around P3
Curve stitching
The two numbers add up to the number of points plus 1.
How to do it
Method
The two numbers add up to the number of points plus 1
6 points an arm: point 2 joins point 6 + 1 − 2 = 5
Another way
Count from the far end
Point 2 joins the 2nd from the far end
In full
Curve stitching makes a curve out of many straight lines. Draw an angle and mark the same number of points, evenly spaced from the corner, on both arms, numbering each arm 1, 2, 3… The 1st point on the upright arm joins the furthest point on the flat arm, the 2nd joins the second furthest, and so on: with n points on an arm, point k joins point n + 1 − k on the other arm, so the two numbers always add up to n + 1. An arm with n points needs n threads. The more points, and the closer together, the smoother the curve.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
In curve stitching every point on the arms gets one thread (a few are drawn). How many threads are there when it is finished?
Show the answer and working
Answer: 9 threads
Each arm has 9 points and each thread joins one point on each arm: 9 threads.
Example 2
Some threads of this curve stitching are drawn. How many more are needed to finish?
Show the answer and working
Answer: 3 threads
12 in all, 9 drawn: 3 more.
Example 3
Follow the pattern in the picture. Point 7 on the upright arm joins which point on the flat arm?
Show the answer and working
Answer: 5
The two numbers add up to 11 + 1: point 7 joins point 5.
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