Предмет: Математика, автор: ashacollkok

Турист проплыв по течению реки по плоту 12 км,возвратился обратно на лодке,скорость которой в стоячей воде 6 км/ч.Найдите скорость течения реки,если известно,что на всё путешествие турист затратил 8 ч.

Ответы

Автор ответа: DariosI

Пусть скорость течения реки V, тогда по течению турист плыл 12/v часов, обратно турист плыл 12/(6-V) часов. Поскольку все путешествие турист затратил 8 часов, то
12/V+12/(6-V)=8
12*(6-V)+12V=8*V*(6-V)
72-12V+12V=48V-8V²
72=48V-8V²
V²-6V+9=0
D=36-4*9=0
V=6/2=3
Ответ скорость течения 3 км/ч

Предыдущий вопрос

Следующий вопрос

Похожие вопросы

Предмет: Физика, автор: lesha7373

Помогите пожалуйста , желательно с дано .
какая масса воды должна кристаллизоваться чтобы в результате этого процесса выделилось такое же количество теплоты,что при крсталлизации 8 кг свинца?

6 лет назад

Предмет: География, автор: Аноним

Срочно!!!! помогитееее !!!!пожалуйста !!!!!

6 лет назад

Предмет: Английский язык, автор: n23032007

Ребят кто знает английский помогите даю 100 баллов
Exercise 1 (20 points).

Open the brackets using Present Simple, Present Continuous, Past Simple or Past Continuous. Write down full sentences.

Sorry, I didn’t help you. I (have) a shower when you phoned.
She tried to explain his problems to her best friend, but he just (not/understand) what she was talking about.
What have you put in my salad? It (taste) absolutely disgusting.
Anna always claimed that she did everything on her own, but for many years no one (believe) her.
It’s a stunning dress, but it (not/belong) to me. I’m just borrowing it for the concert this evening.
Why (you/wear) these sandals? You’ll freeze to death in this cold wind!
Tim’s upset because he twisted his ankle when he (jog) this morning.
While I was staring at the monument, someone (steal) my phone from my bag.
Look! (you/see) that woman standing in the queue? I’m sure I know her.
Tea or coffee? I’m making both, so just say which you (prefer).

Exercise 7 (15 points).

Fill in the gaps with one of the words:

desperate, connecting on, using the Internet, young people, over scheduled, hanging out, communicate, run around, make up, going online

Most everything we think we know about the way our kids are (1) _______ is wrong.

Boyd’s new book, It’s Complicated: The Social Lives of Networked Teens, makes the case that the Internet isn’t nearly as scary to (2) _______ as many parents believe.

Although the image persists that youngsters would rather text than talk, and prefer (3) _______ Facebook than (4) _______ in person, Boyd says this isn’t true. “Most of the teens that I met . . . were (5) _______ for the opportunity to leave their homes to gather with friends,” she writes.

The trouble is that in many communities, young people have less freedom to roam than they once did as they are so (6) _______ and because parents are worried about their safety. “The era of being able to (7) _______ after school so long as you are home before dark is long over,” Boyd claims.

To (8) _______ for this lost freedom, teens have turned to their gadgets. “The success of social media must be understood partly in relation to this shrinking social landscape,” Boyd explains. Facebook, Twitter, Instagram, and other sites “are not only new public spaces; they are in many cases the only ‘public’ spaces in which teens can easily (9) _______ with large groups of their peers.”

One way or another, “teens want to gossip, complain, compare notes, share passions and joke around,” Boyd adds. “They want to be able to talk among themselves—even if that means (10) _______”.

Exercise 6 (20 points).

Make new words from the words in brackets. Use suffixes and prefixes.

I’ve never seen her react so (angry).
Paul behaved (calm).
That is an (polite) boy. He never says ‘Good morning’.
His lecture (bore) the class so everyone fell asleep.
This is a very (bore) subject.
The professional cleaner was very (help). She immediately understood what I needed.
She adopted a (home) cat.
We enjoyed a (success) event. Everything was great!
What a (beauty) painting. Do you know who painted it?
That shark looks dangerous, but it's totally (harm).

6 лет назад

Предмет: Математика, автор: санчоуа

петрик з батьком посадили 8 яблунь. це на 3 більше ніж груш. скільки груш посадили?

9 лет назад

Предмет: Физика, автор: furazhkovalera

поезд массой 2000 т движущийся со скоростью 36 км/ч ,остановился, пройдя после начала торможения путь в 350 м. определить величину тормозящей силы и время торможения

9 лет назад