Покупатель выбрал арбуз весом 6 кг и дал продавцу 500руб. сколько рублей сдачи должен получить покупатель. арбуз-12руб за 1кг

I farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravyI farted with gravy

Весь путь автомобиля примем за единицу (целое).

1) 1 - 5/12 = 12/12 - 5/12 = 7/12 - оставшаяся часть пути;

2) 15/28 · 7/12 = (5·1)/(4·4) = 5/16 - часть пути, пройденного за второй час;

3) 7/12 - 5/16 = 28/48 - 15/48 = 13/48 - часть пути, пройденного за третий час;

4) 5/12 - 13/48 = 20/48 - 13/48 = 7/48 - разница, равная 42 км;

5) 42 : 7/48 = 42 · 48/7 = 6 · 48 = 288 (км) - весь путь автомобиля.

ответ: 288 км.

Проверка:

1) 5/12 · 288 = 120 км - пройдено за 1-й час;

2) 15/28 · (288 - 120) = 90 км - пройдено за 2-й час;

3) 13/48 · 288 = 78 км - пройдено за 3-й час;

4) 120 - 78 = 42 км - на столько меньше пройдено за 3-й час.