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.
1. (Mathematics) the branch of mathematics concerned with numerical calculations, such as addition, subtraction, multiplication, and division. 2. (Mathematics) one or more calculations involving numerical operations. 3. (Mathematics) knowledge of or skill in using arithmetic: his arithmetic is good. adj.