How to divide in the mind

A few decades ago in the regular education schools there was a subject "Oral account". The children were taught to produce in the mind of the basic mathematical operations: addition, subtraction, multiplication and division, which can be considered the most difficult of them.

The division implies a quick search of the maximum of the divider. Method of oral division requires knowledge of techniques reduced the school division and multiplication tables. In addition, you need to train memory to learn to keep in mind all intermediate calculations, especially if the numbers are large.

The expansion of the private for sostavlenie, you need to divide the number by 7 3647. Imagine private as the sum of the numbers 3500 and 147. In this example, the 3500 is the biggest obvious the number, the smaller the source, which is divided by 7 without residue:3647/7 = 3500/7 + 147/7 = 500 + 147/7 = 500 + 21 = 521.

Division "column," in the mind, as in destinyland imagine a sheet of paper and imaginary pencil and make the calculations. This method requires a good visual memory, which, however, it is possible to train a regular exercise program in the account. This method is preferred by many because it is familiar from school days, though not as fast as the previous one.

Division by 10, 100, 1000, etc. This method involves the separation of a corresponding number of commas, starting with the right side of the number. For example, divide the number 567890 10,000:567890/10000 = 56,7890 – branch four zeros.

Division by 0.1, 0.01, etc., This scenario implies a multiplication of 1 with a corresponding number of subsequent zeros, i.e., a decimal fraction upside down. For example, divide the number 78,765 on 0,0001:78,765/0,0001 = 78,765*10000 = 787650.

The division into decimal will kobetamendi her mentally in common, for example, 0.5 for 1/2. Multiply the original number by the denominator and divide by the numerator. For example, divide the number 2250 for 0,75:2250/0,75 = 2250/(3/4) = 2250*4/3 = 9000/3 = 3000.

Dividing by 5, 50, 500, etc. Replace the divisor by the appropriate fraction: 5 = 10/2; 50 = 100/2, etc. Now it is enough to separate the private two decimal places and multiply by 2. For example, divide 1750 on 50:1750/50 = 1750*2/100 = 3500/100 = 35.

Similarly, there is a division by 2, 5, 25, etc.: the divisor is replaced by the appropriate fraction with 4 in the denominator. Of 1.25, 12.5 and so on the fraction with 8 in the denominator:285/2,5 = 285*4/10 = 1140/10 = 114;600/12,5 = 600*8/100 = 4800/100 = 48.