Відрізок А, В, — паралельна проекція відрізка AB на площину о (мал. 249). Знайдіть довжину відрізка Mм1, якщо AA1 = 10 см, ВВ, = 16 см. АА, | BB, | MM, AM : MB = 2 : 1.
Computer pluses: Helps with study, it is possible to use as a training apparatus in the course of formation of educational skills; Gives the chance to support a close connection with friends in other cities; Source of reception of the various information; Creativity freedom (creation of presentations, cards, a music writing, work with photos); Development of logic thinking, ability to the analysis and synthesis; Develops a self-trust, in the abilities to solve various informative problems;
Computer minuses: Problems with sight; Problems with a bearing; Shortage of time for other useful affairs; Narrowing a focus of interest, one-sided personal development; Aggravation of neurotic lines of the person because of excessive attachment to the virtual world; On the Internet there are ready abstracts, compositions, homeworks which can be copied blindly that отупляет and disaccustoms to mental work; Mental loading;
2) 7/8 • 4/5 = 28/40 = 7/10 книги было прочитано еще (когда было прочитано 4/5 остатка).
3) 1 - 1/8 - 7/10 = 40/40 - 5/40 - 28/40 = 7/40 - осталось прочитать, и это соответствует 21 странице.
4) 21 • 40/7 = 3•40 = 120 страниц в книге.
Проверка:
1) 120•1/8= 15 страниц было прочитано сначала
2) 120-15 = 105 страниц осталось прочитать.
3) 105• 4/5 = 84 - страниц прочитано потом.
4) 15+84+21= 120 страниц в книге всего.
Пусть х - количество страниц в книге.
Тогда х/8 - прочитали вначале.
х-х/8 - осталось прочитать вначале.
(х-х/8)• 4/5 - прочитано позже
Уравнение
х/8 + (х-х/8)•4/5 + 21 = х
х/8 + 4х/5 - 4х/40 + 21 = х
х - х/8 - 4х/5 + 4х/40 = 21
40х/40 - 5х/40 -32х/40 + 4х/40 = 21
7х/40 = 21
х = 21•40/7
х = 120 страниц было в книге.
Helps with study, it is possible to use as a training apparatus in the course of formation of educational skills;
Gives the chance to support a close connection with friends in other cities;
Source of reception of the various information;
Creativity freedom (creation of presentations, cards, a music writing, work with photos);
Development of logic thinking, ability to the analysis and synthesis;
Develops a self-trust, in the abilities to solve various informative problems;
Computer minuses:
Problems with sight;
Problems with a bearing;
Shortage of time for other useful affairs;
Narrowing a focus of interest, one-sided personal development;
Aggravation of neurotic lines of the person because of excessive attachment to the virtual world;
On the Internet there are ready abstracts, compositions, homeworks which can be copied blindly that отупляет and disaccustoms to mental work;
Mental loading;