Предмет: Математика, автор: ghbdtn

здравствуйте помогите решить пожалуйста задачу. На трёх полках стоят книги . На первой полке 1/4 всех книг, на второй полке 40% всех книг, а на третьей полке 28 книг. Сколько книг стоят на трёх полках.пожалуйста!!!

Ответы

Автор ответа: GUGUCHA

Пусть х- число всех книг на трёх полках. Тогда 0,25х- на первой полке, 0,4х- на второй полке. Составим уравнение:

0,25х+0,4х+28=х

0,65х-х=-28

-0,35х=-28 |:(-0,35)

х=80 (книг)- было на трёх полках.

Ответ: 80 книг.

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