Definition and calculation methodThe numbers which are on the left of the number 0 are called negative numbers.The numbers which are on the right of the number 0 are called positive numbers. Integers are every positive and negative numbers. To add or subtract two positive or negative numbers : 1. You place the first number on the line above. 2. Then if there is a + sign you move towards the right, if there is a - sign you move towards the left. 3. You move towards the right or towards the left of the second number. ExamplesTo calculate 1 + 3, you first place the number 1 on the drawing (in green on the picture), then as there is the sign + you move towards the right and then as there is the number 3 you move 3 steps forward. You land on the number 4. Therefore 3 + 1 = 4. This method also works for more complicated calculations. To calculate - 3 - 2 , you first place the number - 3 then as there is the sign - you move towards the left and then as there is the number 2 you move 2 steps on the left. You land on the number - 5 therefore - 3 - 2 = - 5. To calculate 4 - 5 the result is not 1 because if you have a 4 dollars and you spend 5 dollars you cannot have 1 dollar left. You place yourself on 4 and you move 5 steps on the left because it is a negative sign -. We land on -1 therefore 4 - 5 = -1. Final example : to calculate - 5 + 3, you place yourself on - 5 and you move forward 3 steps on the right (sign +), you land on the number -2, so - 5 + 3 = -2. When the signs follow each other : When two + signs follow each other, it is as if there were only one + sign + If a - sign and a + sign follow each other or vice versa, it is as if there were a - sign If two - signs follow each other, it is as if there were a + sign. You must always put brackets between two signs which follow each other. Examples : 3 + (+3) = 3 + 3 4 - (+7) = 4 - 7 -2 + (-1) = - 2 - 1 - 5 - (-8) = - 5 + 8 5 - (+6) = 5 - 6 You can complete the last stage of the calculations by drawing the grduated line and following the above method. We respectively get the following results: 6, - 3, - 3, 3, and -1. See also : integers on fmaths.com |