расстояние между двумя пристанями по реке равно 24 км. Моторная лодка прошла от одной пристани до другой, сделала стоянку на 1 час 40 мин и вернулась обратно. Все путешествие заняло 6 2/3 часа(400мин). Найдите скорость течения реки, если известно, что скорость моторной лодки в стоячей воде равна 10км/ч
1час 40 минут= одна целая две трети часа, значит лодка плыла 6 целых 2/3-1 целая 2/3= 5 часов.
пусть скорость теч=х, тогда скорость по теч=10+х, против теч=10-х.
24/10+х + 24/10-х =5
240-24х+24х+240=50х^2 +500 - 50
480=5х^2 +500
х^2=4
х=2
ответ 2 км/час
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