114
Properties of segments
Textbook Part 4, pp. 8–9
GoalCompare segments in different ways; know that the parts of a segment add up to the whole.
New words
by eye · ko‘z bilanby laying one on the other · ustma-ust qo‘yibby measuring · o‘lchab
Explanation
Segments can be compared in three ways: 1) by eye (roughly); 2) by laying one on the other; 3) by measuring — the most accurate. If point C lies on segment AB, then AC + CB = AB.
Worked examples
AC = 3 cm, CB = 5 cm → AB = 3 + 5 = 8 cm.
AB = 9 cm, AC = 4 cm → CB = 9 − 4 = 5 cm (the inverse problem).
Class activity
Comparing with string: children lay string along two curvy paths, then straighten the string on a ruler to find each length.
Practice
1
AC = 6 cm, CB = 3 cm. AB = ?
9 cm
2
AB = 12 cm, AC = 7 cm. CB = ?
5 cm
3
Which way of comparing is most accurate?
Measuring
4
A rug needs fringe of 2 cm + 3 cm + 2 cm + 3 cm along its edges. Total?
10 cm