How to find deductible

How to find deductible

Any task on subtraction is the return in relation to simple arithmetic action to addition. They are more difficult for development. Especially in what it is required to find deductible.

It is required to you

  • - sheet of paper;
  • - handle;
  • - examples;
  • - pencils;
  • - handles.


1. Remember that subtraction is one of four main arithmetic actions at which on two numbers the third is found, giving in the sum with the second the first. If to consider subtraction as action the return to addition, then it turns out that at subtraction define one of composed (it in subtraction is called a difference), proceeding from the sum two composed (call reduced) and another composed (call deductible).

2. To acquire the rule of finding of the unknown deductible, use the different simple and not really methodical receptions accepted in mathematics. First of all consider equality: 10 – 6 = 4. For a start assume what in an example with the unknown is reduced, that is X – 6 = 4. It is simple to find it, it is necessary only to 6 to add 4: 6 + 4 = 10.

3. Then consider the equation when it is unknown deductible: 10 – X = 4. Pay attention that follows from subtraction definition as arithmetic action that 10 is the sum two composed 6 and 4: 10 = 6 + 4.

4. Remember the rule that if from the sum two composed to take away one of these numbers, other composed as a result will be found. Means to find unknown to X which in the given example is deductible it is necessary from 10 to take away 4: 10 – 4 = 6. Deductible it is found, X = 6.

5. Now find unknown deductible in other equation. For example, 61 – and = 29. Argue, as well as in the previous equality. Consists in number 61 which is the sum of two composed 29 and other number and – unknown deductible. And that to find the last, take away from 61 numbers 29: 61 – 29 = 32. Deductible it turned out equal 32. Check correctness of the solution of the equation, having substituted instead of the unknown and the found number: 61 – 32 = 29. Equality true, so and = 32.

6. Set the gained knowledge by means of the solution of tasks with use of objects and visual aids (handles, apples, pencils and other make-shifts). For sure development of material solve more equations. Learn by heart the rule of finding of the unknown deductible which says: to find unknown deductible, it is necessary from reduced to take away a difference.

Author: «MirrorInfo» Dream Team