Primary 5 math problems, urgent !! High Rewards!!

Iron sheets are needed to find the surface area, and the top and bottom surfaces of the water pipe are empty.

That is, find the area of the four faces: 2 * (length * height + width * height) = 2 * (4 * 8 + 8 * 12) = 256 square centimeters.

Solution: To find the area of the iron sheet used, it is to find the surface area of this rectangle, as follows.

432 (square centimeters).

Therefore, to make a section of such a liushui pipe, you need at least 432 square centimeters of iron sheet.

The first option.

2*(4+8)*12=288 (square centimeters).

The second option.

2*(4+12)*8=256 (square centimeters).

The third option.

2*(8+12)*4=160 (square centimeters).

The third option is the least.

A: A minimum of 160 square centimeters is required.

Surface area = (length * width + length * height + width * height) * 2 - length * width * 2 (because it is a water pipe, it should be subtracted).

Length * Height + Width * Height) *2

256 (square centimeters).

Area = 2 * (length * width + length * height + width * height).

352 cubic centimeters.

Upstairs is whether the water pipe is good or not, it should be 2 * (4 * 12 + 12 * 8) = 288 square centimeters.

s=(ab+ah+bh)×2

366 (square centimeters).

A: A minimum of 366 square centimeters of iron sheet is required.

The idea goes like this: the first two numbers: 3 or 4, they and 6 can be divided by a positive number to equal an integer. So they can ignore it and let 6 come and do their delegates.

And then that's left with 5 and 6, and that multiplies them and subtracts 1 from the number you get, haha. Isn't that the final answer, 5*6=30

At this time, you substitute the calculation, and you will find that you can't do this group of 4.

Then you try doubling the multiplier: 30*2=60

Substituting into each group, discovering. It's all in line with.,That's 59 this.。。。

Big brother is here to help you, set the side length of the cube to A, and reduce the side length by 2 cm to A-2

centimeters. Its original surface area is 6 times a square, and the surface area after the side length is reduced is 6 times (a-2) squared, and the surface area is reduced by 40 cm, so 6*a 2-6*(a-2) 2=40, you can calculate a,

1. Fill in the blanks.

1. The fractional unit of one-eighth and three-eighths is (1 8), it has (11) such units, and then filling in (1) such units is the smallest composite number.

2. The denominator is 15, and the sum of all the simplest true fractions is (4).

plus 2 tenths, there are a total of (6) tenths, that is, tenths (six), and the simplest fraction is (3 5).

4. One-third more than five-sixths of a kilogram is (7 6) kilograms, and five-eighths of a kilometer is a quarter of a kilometer less than (7 8) kilometers.

5. Use fractions to represent the following numbers [note that fractions are used and can be turned into the simplest fractions!!

1 hour 25 minutes = (1 5 14) hours 4 kg 25 g = (4 1 40) kg.

3 square meters, 15 square decimeters = (3 and 3, 20) square meters, 2 cubic meters, 18 cubic decimeters = (2 and 9, 500) cubic meters.

6. A simplest fraction Its numerator is reduced to one-third of the original, and the denominator can be about two-sevenths after expanding by 5 times, and the original fraction is (30 7).

Four-fifths of m is as long as one-fifth of (4m).

8. Divide 4kg of apples equally among 5 children, each person can get (4 5) kg, and each person can get 1 kg of (5) (4). Here you can fill in the minimum score, fill in the minimum score].

1. 1/8 11 21 2, 4 and 10/15.

3. 6 out of 10 3 out of 5 4 7 out of 6 7 out of 8.

5. One and a quarter of an hour, four and a forty a kilogram, three and two-twentieth of a square meter, two and five and a nine.

6. 30 out of seven.

7. Four meters. 8. Four-fifths of a kilogram and four-fifths of a kilogram.

\8 11 5

m 5 5 1 hope this helps, thanks.

For the first time get two rectangles.

The second time you get a rectangle and two squares.

The third time you get three rectangles and one square.

The fourth time you get two rectangles and three squares.

The hundredth time, fifty rectangles, fifty-one squares.

The hundredth time, fifty rectangles, fifty-one squares.

After 100 times, you get 50 rectangles and 51 squares. The following figure shows that the number of paper-cuts is 1 2 3 4 5 6 7 8 9 10 ...n (when even) or n (when singular).

Rectangle 2 1 3 2 4 3 5 4 6 5 ...n 2 or (n + 3) 2

Square 0 2 1 3 2 4 3 5 4 6 ...n+2) 2 or (n-1) 2

Rectangle: (99-1) 2+1=50.

Square: 100 2 = 50.

The odd number is two identical rectangles, the even number is two identical squares, and 100 is an even number, so are two identical squares.

50 rectangles and 51 squares.

The observed rectangle changes by order of 2,1,3,2,4,3, the rule of squares is: 0,2,1,3,2,4, and the change of even times is: 1,2,3,

100 times is an even number, which is the 50th even number from the second time, so the rectangle is 50 In the same way, the law of even number changes of a square is: 2, 3, 4, so the 50th even number is 51, and the square is 51

This question can be explained in the form of a list.

Number of squares Number of rectangles Total number.

Draw your hands on it, and you can list the above table in just a few times. Looking at the table above, we can see that at the even number of times, the square is always one more than the rectangle, and the total number of squares and rectangles is 1 more than the number of cuts, so when the number of cuts is 100 times, the total number should be 101, so there are 51 squares and 50 rectangles.

Cut a rectangle 100 times at a time, which is 100 rectangles.

Squares -- 2 squares at a time, 100 times, 200 squares.

Fifty rectangles and fifty squares.

v=a×a×a

125 (cubic decimeter).

Answer: Water depth. and a common multiple of 9 has ......

The conditions say that the number of people required is more than 70, that is, 72 people) A: At least 72 people participate in the singing and swimming competition.

1260 (cubic meters).

1260 3 = 420 (minutes).

420 minutes = 7 hours.

A: It takes 7 hours to drain the water.

1 5*5*5/

2 The number of people is a multiple of 12 and 9 is 72.

1.First find the volume of the cube (count it yourself), and then divide it by the width and length of the cuboid 2At least 72 people.

Multiply 30 by 20 and divide by 3.

Study hard, you can't always wait for others to solve the problems you don't know, and you have to think about it yourself ( o )

(1) 5 times 5 times 5 divided by 8 divided by 25 to get the result. This question has nothing to do with 7.

cubic decimeters.

125 (8 25) = decimeter.

and 9 to a least common multiple of 36

Common multiples of 70, the minimum is 36 2 = 72

At least 72 people participated in the singing competition.

Cubic meters 1260 3 60 = 7 hours.

*Stands for multiplication Stands for division (sorry, won't hit).

1. 25cm= （5*5*5+8* 5*52.No.

Multiples of 108 people.

Minutes = 7 hours.

*5*5=125 (cubic decimeter).

125 (8*25 10)=dm)).

and the least common multiple of 9 36, the requirement in the question is more than 70 people, so it is 36 * 2 = 72 people.

20*min) 420 mins = 7 hours.

5*5*5/8/

The least common multiple of 12 and 9 is 36, and the number of 70 is 72 (36*2).

Hours (420 minutes) 30 * 20 * minutes = 7 hours.

1.The volume of water in the box is equal to the volume of water in the cube. (5×5×5)÷(8×25)

2.The main thing is to find the least common multiple of 12 and 9 first. 12 = 3 4 9 3 3 3 3 3 36 Considering that the number of people should be above 70, so 36 2 72 people? Divide.

1.The volume of water remains unchanged and is:

5 5 5 = 125 cubic decimeters.

Water depth: 125 (8 25) = decimeters.

and 9 to a least common multiple of 36

Common multiples of 70, the minimum is 36 2 = 72

At least 72 people participated in the singing competition.

3.Volume of water:

30 20 cubic meters.

Finishing required: 1260 3 60 = 7 hours.