Due to the development of technologies the need to make mathematical calculations in mind disappeared. However division without calculator, the computer and paper with a pencil is a good training for a brain and confidence in the forces at emergence of unforeseen circumstances.
Instruction
1. Several decades ago at usual educational schools there was a subject "Oral Account". Children studied to make the main mathematical operations in mind: addition, subtraction, multiplication and division which can be considered the most difficult of them.
2. Division assumes fast search of the maximum divider. The method of oral division demands knowledge of methods of the reduced division and the school multiplication table. Besides, it is necessary to train memory to learn to keep in mind all intermediate calculations, especially if figures big.
3. Decomposition private on a sostavlyayushchiyenaprimer, you need to divide number 3647 into 7. Present private as the sum of numbers 3500 and 147. In this example 3500 – the largest obvious number, smaller initial which is divided into 7 without the rest: 3647/7 = 3500/7 + 147/7 = 500 + 147/7 = 500 + 21 = 521.
4. Division by "column" in mind as in detstvemyslenno submit the sheet of paper and the imagined pencil make calculations. This method demands good visual memory which, however, can be trained regular exercises in the account. This method is preferred by many since it is well familiar since school times, though not such fast as previous.
5. Division on 10, 100, 1000, etc. This way assumes office of the corresponding number of commas, since the right side of number. For example, divide number 567890 into 10000:567890/10000 = 56.7890 – office of four zero.
6. Division on 0.1, 0.01, etc. This option assume multiplication by 1 with the corresponding number of the subsequent zero, i.e. overturn decimal fraction. For example, divide number 78.765 into 0,0001:78,765/0,0001 = 78.765*10000 = 787650.
7. Division on decimal you drobzamenit it mentally on usual, for example, 0.5 on 1/2. Increase initial number by a denominator and divide into numerator. For example, divide number 2250 into 0.75:2250/0.75 = 2250 / (3/4) = 2250*4/3 = 9000/3 = 3000.
8. Division on 5, 50, 500, etc. Replace a divider with the corresponding fraction: 5 = 10/2; 50 = 100/2, etc. Now it is enough to separate at private two signs after a comma and to increase by 2. For example, divide 1750 into 50:1750/50 = 1750*2/100 = 3500/100 = 35.
9. By the similar principle there is a division on 2.5, 25 and so forth: the divider is replaced with the corresponding fraction from 4 in a denominator. 1,25, 12,5 and so forth – on fraction with 8 in a denominator: 285/2.5 = 285*4/10 = 1140/10 = 114;600/12,5 = 600*8/100 = 4800/100 = 48.