Primary 2 math problems, solving, 2nd grade math problem solving

I'm a whale, and the biggest and biggest whale in the ocean, the blue whale, aka the razor whale.

I live in the ocean, I have many brothers and sisters, and I have many friends, swimming in the deep ocean.

When I am happy, I will float to the surface of the sea and say hello to the blue sky and white clouds; When I was upset, I dived to the bottom of the sea, and no one looked for me. When the wind and the sun were beautiful, I swam to the sea, surfaced, looked at the land and mountains from afar, and thought: Our ancestors came from **?

If you want to talk about my ancestors, you have to start from 100 million years ago.

At that time, the ancient total fin fish evolved into amphibians, reptiles, birds and mammitals, and it was not until 70 million years ago that our ancestors differentiated from the mammals.

At that time, the ancestors were still on land, and later occupied the ocean, lived in the shallow sea, and finally adapted to the life of the ocean, which evolved into the whale we have now.

We are so big, our bellies must be big, and what are we going to eat with such a big belly? When I eat small fish and shrimp, I first stretch my stomach wide and swallow it in my mouth with the seawater, then close my mouth and press the water out to swallow only the food. Why do we eat small fish and shrimp?

Because we have no teeth and can't chew food, we can only eat small fish and shrimp, although they are small, but there are a lot of them, so we don't have to worry about hunger.

Do you know? My lungs weigh about 1,500 kilograms, can breathe 15,000 liters of air, can stay underwater for 18 minutes, and when I breathe, due to the excessive pressure, not only is the sound loud, but there will also be a "fountain" on the sea, which is beautiful! It sprays more than ten meters high, and then scatters and falls on the sea, making a splash, looking at it from a distance, just like fireworks in a festival, very beautiful!

This is me, the mammital whale that lives in the deep sea, and a good friend of you humans. Map.

This data is ** on the map, and the final result is subject to the latest data on the map.

I don't even give a single number, how can I calculate it.

Isn't this a mistake in writing without chain auspiciousness?

He had 28 books, and 19 of the half of the fairy tale books that Nayan had left.

In other words, it's not"Half of the fairy tale books" = "the number of books taken" as shedIs it?

After 28-19 = 9, multiply by 2 to get the number of fairy tale books.

28-19 = 9 (books) (half of fairy tale books).

9*2==18 (book).

The answer is: 21 + 18 = 39 (question).

39-30=9 (person).

Answer: There are 9 people who got both questions right.

This is the 2nd grade mathematics wide-angle problem There are 21 people who do the first question correctly, and 18 people who do the second question correctly, why is the total number of people more than 30, because those people do both questions correctly, so the column formula 21 + 18-30 = 9 people.

There were 30 people, 21 of whom got the first question right, and 18 of whom got the second division right. Therefore, if both questions are correct, there will be at least 21 + 18-30 = 9 people, and if both questions are correct, there will be a maximum of 18 people.

The principle of repulsion.

9 people who got both questions right.

The number of people who do both questions and the number of people in the class is 21 + 18-30 = 9

9 people will do it.

9 people did not get the first question right. 12 people did not get the second question right. 12 + 9 = 21 30-21 = 9, indicating that at least 9 people have both questions correct.

30-21=9 (person).

18-9=9 (person).

A: There are 9 people who did it right.

21 + 18-30 = 9 (people).

At least nine people got both questions right.

21+18-30=9

This is the principle of repulsion. You can draw a diagram:

For the principle of repulsion, you can search the Internet again.

Solution: Set up two people to read page x on the first day.

The rest of the (580-x) page was not read.

Mickey left the (720-x) page unread.

So the difference between Mickey and Honghong is (720-x)-(580-x)=720-x-580+x=140 (pages).

A: The difference is 140 pages.

Because the number of pages read is the same, the difference between the number of pages left unread is the same as the difference between the number of pages in the whole book.

There are 140 pages left unread.

If I read x pages on the first day, there are 580-x left in the red book. Mickey's book has 720-x pages left, and the difference between the two is 720-x-(580-x) = 720-580 = 140 pages.

Because I watched the same amount on the first day, the difference is the same as when I didn't watch it.

Therefore 720-580 = 140

The math in the second grade was even harder than my 2 years higher.

The two watched as much.

I: 4 3 = 12 pages.

Sister: 2 + 4 + 6 = 12 pages.

Hope it helps.

If you have any questions, you can follow up.

Thank you.

1+4=5

The key is to establish a multiplication relationship in these 6 numbers. 1 * any number = any number, so that the multiplier and the result number are the same, is not possible.

2*3=6, 2*4=8, when the multiplier is greater than 3, the resulting number is greater than 6, and it is also not allowed.

3*4=12, which is obviously greater than 6, then among these 6 numbers, only 2*3=6 can establish a multiplier relationship.

Then the remaining three numbers, 1, 4, and 5, need to establish an addition relationship, that is, 1+4=5

Yes, the correct answer is.

2）x（3）=（6）

Only 2x3=6 of the multiplication formula satisfies the requirements, and there are several of the additive formulas, such as 1+2=3 1+3=4 1+4=5 1+5=6 2+4=6 But the multiplier uses 2 3 6, and only 1 4 5

The number to the left of the equal sign can also be reversed.

3）x（2）=（6）

Only 2x3=6 of the multiplication formula satisfies the requirements, and there are several of the additive formulas, such as 1+2=3 1+3=4 1+4=5 1+5=6 2+4=6 But the multiplier uses 2 3 6, and only 1 4 5

2）x（3）=（6）

8 times the number of the upper row is the sum of the two numbers in the lower row.