Extracurricular development of mathematics for the fifth grade, and mathematical thinking developmen

Solution: Analysis, for every two people who share a rice bowl, each person uses 1 2 rice bowls, three people share a vegetable bowl, each person uses 1 3 vegetable bowls, and four people share a soup bowl, each person uses 1 4 soup bowls.

1 2+1 3+1 4 is the bowl used by one person, and everyone is a total of 26 bowls, and how many people are there in the expedition: column:

24 (person).

Solution: Set the number of people x

A total of x 2 rice bowls, x 3 vegetable bowls, and x 4 soup bowls were used.

We get x 2 + x 3 + x 4 = 26

13x/12=26

x=24

This question is a common multiple problem.

From the title, it can be seen that the number of expeditions is a common multiple of 2, 3, and 4.

And their least common multiple is 12, that is, 12 people need to use 6 rice bowls, 4 vegetable bowls, and 3 soup bowls, a total of 13.

There were 26 bowls in total, and all of them had 26 13 * 12 = 24 people.

How many bowls do 12 people use, 12 2 = 6, 12 3 = 4, 12 4 = 3, a total of 6 + 4 + 3 = 13, 26 13 = 2, 2 * 12 = 24. A total of 24 people.

Because every two people share a rice bowl, three people share a vegetable bowl, and four people share a soup bowl, so the number of people must be a multiple of 2, 3, 4, first find the least common multiple of 2, 3, 4, that is, 12, then according to 12, you need to use a bowl 12 2 + 12 3 + 12 4 = 13, and because a total of 26 bowls are just enough, 26 is twice as many as 13, so the total number of people is 12 * 2 = 24 people.

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2. The numerator of a simplest fraction is expanded by 4 times, and the denominator is reduced by 3 times to obtain 10, then this simplest fraction is ( ).

3. There are ( ) divisors of 360, and the sum of these divisors is ( ).

4. A math test, the average score of the whole class in the May 1st class is 91 points, the average score of the boys is 89 points, the average score of the girls, there are 24 girls in this class, and the boys ( ) people, 5. Guangming Bookstore sold a total of 120 books A and B, 5 yuan per book for a book, and a book for each book.

6. There is a class of students who go rowing, they calculated, if one boat is added, exactly 6 people will sit in each boat, and if one boat is reduced, there will be 9 people in each boat, and there will be a total of ( ) students in this class.

7. Fill in the numbers according to the rules, (

8. A natural number is divided by 3 by 1, by 5 by 2, by 7 by 3, and the smallest natural number is ( ).

9. If we know that May 1, 2005 is a Sunday, then October 1 of that year is a week ( ).

10. The length and width of the rectangle are prime numbers, and the circumference is 36 meters, so the area of the rectangle is.

square meters. 11. Xiao Ming walks 60 meters per minute from home to school, then he will be 5 minutes late, if he walks 90 meters per minute, then he can be 4 minutes in advance, and the distance from Xiao Ming's home to school is ( ) meters?

12. Xiao Ming has a movie ticket with rows of 10 to 40, the common divisor of the number of rows and seats of this ticket is 13, and the least common multiple is 72.

13. A rectangular timber with a square cross-section, the surface area is 118 square centimeters, after sawing off a cube, the surface area is 54 square centimeters, and the surface area of the cubic timber sawed is ( ) square centimeters.

After transporting 24 tons to B, A leaves 120-24 = 96 tons of loose cars.

75% of A is 72 tons.

B's 2 3 is 72. Therefore, B is 72 divided by 2 3 = 108 B is 108-24 = 84 tons.

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Cream popsicle: 28 25 = yuan) fruit popsicle: yuan) yuan) yuan) yuan) yuan).

Cream popsicle: 28 25 = yuan) yuan).

Fruit popsicles: yuan) yuan).

75+90)-(RMB).

Minimum, Max.

Minimum, Max.

Minimum, Max.

Triangle area formula: base multiplied by height divided by 2Therefore, the area of the original triangle is 1 2ah, and the area of the new triangle is 1 2(a+5)h, and the area of the new triangle minus the area of the original triangle is equal to 5 2h, that is, it has increased by 5 2h square meters.

The area of the new triangle is increased by 5 h 2 = square meters. (Increasing the area is the shaded area in the figure).

s1=ah÷2

s2=（a+5）h ÷2= ah÷2 +5/2hs2-s1= 5/2h

The new triangle has increased by 5 2h square meters.

By "the distance is a thousand meters. A walks 6 kilometers per hour, B walks 4 kilometers per hour, "you know, it takes hours from departure to meeting."

During this hour, the dog is running non-stop. Said to have run 1 kilometer with dogs.

Calculated as: x10=1

The time it takes for the dog to walk is equal to the time when the two people meet, and the time of meeting is the total distance divided by the sum of speed, i.e.: 1 divided by (6+4) = hours. Then the distance that the dog runs is 10 times equal to 1 kilometer.

In fact, the distance traveled by the two is the distance that the dog runs.

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