We cannot take half of 9 people. The even numbers, then, are the numbers divisible by 2: 2, 4, 6, 8, and so on. The odd numbers are 1, 3, 5, 7, and so on. If you do not know half of some even number, you can find it by decomposing it mentally into two even numbers whose half you do know.
To draw a shape, line or angle accurately using a compass and straightedge (ruler). Sometimes you are also allowed to use a protractor and triangle.
Mathematics. ( 1 of a set in which a combining operation between members of the set is defined) such that performing the operation between members of the set produces a member of the set, as multiplication in the set of integers. ( 2 of an interval) containing both of its endpoints.