3rd Grade Questions. Problem solving in the third grade of primary school

This question can be solved with a multiplier relation.

1. Picture books are 2 times that of science and technology books, and if you look at science and technology books as 1 copy, picture books are 2 copies2. There are 20 more story books than picture books, and the 20 more books are subtracted from the total, and let's assume that there are as many story books as picture books.

Therefore, from the above, it can be obtained that the three books can be divided into 5 parts. 2 copies of picture books, 1 copy of science and technology books, and 2 copies of story book hypothesis.

That is: 245-20 = 225 (book) 225 5 = 45 (book) picture book: 45 times 2 to get 90, 90 picture books, 45 science and technology books, story book 90 + 20 = 110 (book).

Set the science book to x:

Picture book = 2x;

Storybook = 2x+20;

So it is: 2x+x+2x+20=245

5x=245-20

5x=225

x=225/5

x=45 so there are 45 science books, 90 picture books, and 110 story books.

I don't know if you've taught equations.

Science books, picture books, and storybooks are ABC respectively

a+b+c=245

b=2ac-b=20

The most basic ternary equation. The solution is: a=45, b=90, c=110.

Analysis: From 245 to 20 books, the number of storybooks and pictures is equal, which is twice as many as science and technology books. In other words, the sum of storybooks and picture books is 4 times that of science books. Then 245-20 is 5 times as much as a science book.

So the column: (245-20) (2+2+1)=225 5=45 (Ben).

45x2=90 (book).

90 + 20 = 110 (Ben).

A: There are 45 science and technology books, 90 picture books, and 110 story books.

Estimate: 402 is approximately equal to 400

98 is approximately equal to 100

The final answer is 304

400-100 Each number is reduced to an integer.

Liu Yin's family has 200 sheep, including 125 black sheep and 146 ewes.

Solution: There are 146 ewes, then there are 200-146 = 54 rams, and the rams are all black, so the number of black ewes = 125-54 = 71 (ewes).

A total of 1,235 people in Wuchi Village have the right to vote, and in a village head election, there are only two electors, A and B, of which 591 voted for A, and 96 people think that both voters are not good enough and give up voting.

Number of votes for B = 1235-96-591 = 548 (votes) < 591 (votes), so A is elected.

Calculate first, and then change the question according to the requirements.

1.Changed a number to a three-digit difference.

Change the number 8, which has been subtracted by thousands of digits, to 4

2.Change one more number so that the difference is two digits.

Change the number 8 to 9 by a few hundred digits

1. There are 71 black ewes, and there are x black ewes, because there are 125 black sheep, and except for the black ewes, the rest are all black rams, so there are 125-x black rams.

If all the rams are known to be black, the number of rams is 125-x black rams. There are 200 all rams plus all ewes, so there is 146+(125-x)=200, and x=71 is solved.

2. If A is elected, what is sought is the number of votes obtained by B, and then the number of votes obtained by A and B is compared, and the one with the highest number of votes is elected.

A total of 1,235 people are known, and 96 people abstain, so there are a total of 1,235-96 = 1,139 valid votes.

Because A has 591 votes and another person cannot vote for 2 people at the same time, B gets 1139-591 = 548 votes.

591>548, so A was elected.

3. (1) If it is not changed, the difference is 4135 with four digits, so if the difference becomes a three-digit number, it can only be changed by 1,000 digits.

So it can be 8000-7865 or 4000-3865

2) If it is 8000-7865, it is necessary to change the 100 digits to 8000-7965;

If it is 4000-3865, it becomes 4000-3965.

ps: If you consider negative numbers in the third question, you can get the answer in the same way, I hope it can help you.

2.B has a vote: 1235-591-96 So A candidate was elected.

…Because 09 is a normal year, 367-365 = 2 (only), so there are at most 3 white rabbits born in one day, and there are 31 days in December, 63 21 = 3 (only), so at least 3 gray rabbits are born in one day.

In 2009, there were 365 days, if 1 white rabbit was born every day, then there were 367-365 = 2 white rabbits, and these 2 white rabbits could be born on any day of the 365 days, so at least 2 white rabbits in Uncle Zhang's family were born on the same day, and at most 367 were born on the same day (although it is not realistic).

There are 31 days in December, and according to the previous method, at least 63 21 = 3 gray rabbits are born on the same day.

200-10 = 190 pcs.

50x2=100pcs.

190-100) 30=3 people.

2 adults, 3 children.