Mikhaylo Lomonosov wrote: "The mathematics already then should be learned that it puts mind in order". This statement of the great Russian scientist is confirmed by centuries – the solution of mathematical and logical tasks as well as possible develops intelligence, promotes increase in level of logical thinking. Therefore, psychologists recommend for improvement of progress, for development of nonverbal intelligence, sharpness, non-standard, creative thinking to solve various puzzles, riddles, rebuses, uncommon tasks with children. The present article is devoted to the solution of one of such tasks.
It is required to you
- Paper, handle
Instruction
1. Statement of the problem: How to receive 20 by means of four nine, using at the same time only signs of arithmetic actions? 9 9 9 9 = 20
2. There are two solutions of this task. One - absolutely simple, available to the school student familiar with multiplication/division: 99/9+9=20 or 9+99/9=20 that, actually, is the same example.
3. And here the second decision – more difficult and more beautiful, available already only to the senior as here it is necessary to know what it is a root square of number and a number factorial. The second solution of an objective seems at first sight extremely difficult, but actually gives in even to the oral account: (((√9)!)!) / ((√9) *9+9) = 20nizhe all intermediate calculations are presented: Numerator: √9=33! =1*2*3=66! =1*2*3*4*5*6=720znamenatel: 9=33*9=2727+9=36polnostyyu all example: (((√9)!)!) / ((√9) *9+9) = ((3!)!) / (3*9+9) = (6!) / (27+9) = 720/36 = 20chto it was also required in a condition.