Предмет: Математика, автор: 0ЕваШмидт0

Помогите, срочно, очень надо! Для детского сада купили 20 пирамидок двух видов: по 7 и по 5 колец. У всех этих пирамидок всего 128 колец. Сколько пирамидок каждого вида купили?

Ответы

Автор ответа: helenaal

2

Обозначим через Х пирамидки с 7-ю кольцами и число колец на них будет 7Х, тогда пятиколечных будет (20-Х) штук, а колец на них:
5(20-Х)=100-5Х.
По условию 7Х+100-5Х = 128; 2Х=28; Х=14
20-Х= 20-14=6;
Ответ: 14 пирамидок с 7-ю кольцами, 6 пирамидок с 5-ю кольцами.
Проверка: 7·14+5·6= 128.

Автор ответа: monstri4ekkkk

2

1) 5(20-х)+7х = 128
100-5х+7х = 128
2х=28
х=28:2
х=14(пир) по 7 колец

2)20-14=6 ( пир)-по 5 колец

Ответ:14 пер.по 7;6 пир. по 5

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