2. The two adjacent sides of an isosceles right triangle are 8m and 5m respectively. What's its circumference?

What is the circumference of an isosceles triangle surrounded by strips of 3.20 decimeters and 50 decimeters?

The top angle of isosceles triangle is half of the bottom angle. What are the top and bottom angles of this triangle?

5. equilateral triangles and squares have equal perimeters. The side length of a square is 12 cm. What is the side length of an equilateral triangle?

6. A regular triangular flower bed was built in the happy community, and 15 pots of chrysanthemums were placed on both sides of the flower bed (one pot at each vertex). How many pots are put in a * * *?

7. The two straight lines A and B in the picture below are parallel to each other. Are the heights on the bottom sides of the following four triangles equal in length? Why?

8. The capacity of a bottle of juice is 650ml. How many milliliters is there in a box of juice?

9. Sun Jun poured 1 liter of milk into two identical cups. If the milk in each cup is 300 ml, how many ml of milk is left in the bottle?

10. There are about 5 drops in a millilitre of water, and there are 50 people in the class. How many milliliters 1 drop of water does each person save every day?

11.6 June 14 is World Blood Donation Day. At noon this day, 320 people in a city participated in voluntary blood donation. Voluntary blood donors generally donate 200 ml each time. How many liters is the blood donation?

12. A cold medicine, a bottle of liquid medicine 100 ml, with a dose reminder on it (as shown in the following table). Xiaojun 10 years old. He drank at least one bottle of medicine, and how many times at most?

13.93 gasoline price per liter is around 7 yuan. If a taxi uses 20 liters of gasoline a day, how much will it cost per month (calculated by 30 days)?

14. The school organizes students to participate in tree planting activities. There are 72 plants planted in the low grade, the number of plants planted in the middle grade is three times that of the low grade, and the number of plants planted in the high grade is 20 more than the sum of the plants planted in the middle and lower grades. How many trees are planted in the senior grades?

15. The fruit shop sent 625 kilograms of bananas and 480 kilograms of oranges. Bananas are 25 kg in a basket and oranges are 20 kg in a basket. How many baskets are bananas more than oranges?

16. There are 30 pens in the stationery store, and there are 12 ballpoint pens that are three times more than pens. How many ballpoint pens are there than pens?

17. The vehicle factory wants to produce 1440 tricycles. Originally planned to produce 60 tricycles a day, 80 tricycles were actually produced every day. Can you finish it a few days in advance?

18. Uncle Wang bought a laptop by installment. Make a down payment of 3,000 yuan, and then pay back 245 yuan every month, and pay back * * * 12 months. If you pay at one time, you only need to pay 5200 yuan. How much more does it cost to pay by installment than by lump sum?

19. Xiaojun reads story books, reading 25 pages every day. After reading for five days, he read five more pages, which is exactly half of the book. How many pages are there in this book?

20. There are a bunch of pears and a bunch of peaches with the same weight. Pears sell 17kg, peaches sell 4 1kg. The remaining pears weigh three times as much as the remaining peaches. How many kilograms of pears are there?

2 1. Wang Xiaoliang walks from home to the library to borrow books. Walk every minute/kloc-0.05 meters, and walk to the library in about 28 minutes. How far is his home from the library? (estimated)

22. The speed of sound is 340 meters per second. There is a waist drum team performing in the square. /kloc-What is the sound propagation distance after 0/8 seconds?

There are three classes in Grade Five. There are 45 students in Class One, 48 students in Class Two and 46 students in Class Three. This semester, the school organized social practice activities, and everyone paid 80 yuan's activity fee. How much does this activity cost?

24. Wang planted 125 trees on the hillside last year, and the number of trees planned to be planted this year is 40 times less than last year. How many trees are planned to be planted this year?

25. The experimental primary school bought 78 sets of school uniforms of the same size, including 95 yuan for each coat and 80 yuan for each pair of trousers. How much did you spend on these school uniforms?

26. Zhang Ping plans to travel to Beijing in August. The estimated expenditure is as follows:

Round-trip train ticket (RMB), food (RMB/day), accommodation (RMB/day), tickets and shopping (RMB/day)

550 40 120 200

If you stay on the train for 2 days, you have to call 15 days.

(1) Please calculate how much the tickets and shopping will cost.

(2) How much does the meal cost?

Reference answer:

1. 150÷3=50 (cm)

The length of each side of this equilateral triangle is 50 cm.

2.8+5+5 = 18 (m)

A: Its circumference is18m.

3.20+50+50 = 120 (decimeter)

Answer: The circumference of an isosceles triangle is 120 decimeter.

4.180 ÷ (1+2+2) = 36 36× 2 = 72 (times)

A: The top angle of this triangle is 36 and the bottom angle is 72.

5. 12×4÷3= 16 (cm)

Answer: The length of an equilateral triangle is 16 cm.

6. 15× 3-3 = 42 (basin)

A * * * put 42 pots.

7.a: These heights are equal in length. Because the height on the base of these four triangles is the distance between this group of parallel lines, and the distance between parallel lines is equal everywhere.

8.650× 12=7800 (ml)

A: A box of this juice weighs 7800 ml.

Please adopt it, O(∩_∩)O Thank you. Please keep asking questions.

9. 1L = 1000ml

1000-300× 2 = 400 ml

There is still 400 ml of milk in the bottle.

10.50÷5= 10 (ml)

A: Yes 10 ml.

1 1.320×200=64000 (ml)

64000ml = 64L

A: The blood donation is 64 liters.

12. (1)100 ÷12 ≈ 8 (times)

It will take him at least eight times to finish a bottle of medicine.

(2) 100÷8≈ 12 (times)

A: It takes him 12 times to finish a bottle of medicine.

13.7×20×30=4200 (yuan)

A: 4,200 yuan a month.

14.72+72× 3+20 = 308 (tree)

A: 308 trees were planted in the senior grade.

15.625/25-480/20 =1(basket)

A: There are more bananas than oranges 1 basket.

16.30× 3+ 12-30 = 72 (branch)

A: There are 72 more ballpoint pens than pens.

17.1440 ÷ 60-1440 ÷ 80 = 6 (days)

A: It can be completed six days in advance.

18.300+245×12-5200 = 740 (yuan)

A: Installment payment costs more 740 yuan than lump sum payment.

19.(25× 5+5 )× 2 = 260 pages

This book has 260 pages.

20. (41-17) ÷ (3-1) × 3 = 36 (kg)

There used to be 36 kilograms of pears.

21.105× 28 ≈100× 30 = 3000 (m)

3000 meters =3 kilometers

His home is about 3 kilometers away from the library.

22.340× 18=6 120 (m)

A: The sound propagation distance is 6120m.

23.45+48+46 = 139 (person)

139× 80 =11120 (yuan)

A: The cost of this activity is 1 1 120 yuan.

24.125× 6-40 = 750-40 = 710 (tree)

A: It is planned to plant 7 10 trees this year.

25.(95+80) × 78 = 13650 (yuan)

A: It cost 13650 yuan to buy these school uniforms.

26. (1) 200×15 = 3000 (yuan)

A: Tickets and shopping cost 3,000 yuan.

(2) (15+2) × 40 = 680 (yuan)

A: We need food, 680 yuan.

Knowledge points in the second volume of mathematics in the fourth grade of primary school by People's Education Press

(1) Four operations:

1、 ? Operation sequence: 1. In the formula without brackets, if there is only addition and subtraction or only multiplication and division, it should be calculated from left to right.

2. There are addition, subtraction, multiplication and division in the formula without brackets, so multiply and divide first, then add and subtract.

3. When there are brackets in the formula, the brackets should be calculated first.

2、 ? Addition, subtraction, multiplication and division are called four operations.

3、 ? Operate 0: 1, and add 0 to a number to get the original number.

2. Multiply any number by 0 to get 0.

3,0 cannot be divided. 0 divided by a nonzero number equals 0.

0÷0 can't get a fixed quotient; 5÷0 can't get the business.

(2) Location and direction:

1, according to the direction and distance to determine or draw the specific position of the object. (Drawing and measuring scale and angle)

2. Relativity between positions. The mutual positional relationship between two objects will be described. (Determination of observation points)

3. Draw a simple road map.

(3) Operation method and simple operation:

1, law of addition operation: 1, additive commutative law: two numbers are added, the addend positions are exchanged, and the sum is unchanged.

a+b=b+a

2, the law of addition and association: three numbers are added, you can add the first two numbers first, and then add the third number; Or add the last two numbers first, and then add the first number, and the sum remains the same. (a+b)+c=a+(b+c)

These two laws of addition are often used together.

For example:165+93+35 = 93+(165+35) What is the basis?

2. The essence of continuous subtraction: one number subtracts two numbers continuously, which is equal to the sum of this number MINUS those two numbers.

a-b-c=a-(b+c)

3. Law of Multiplication: 1, Law of Multiplication and Exchange: When two numbers are multiplied, the position of the exchange factor remains unchanged.

Answer? × ? b？ = ? b？ × ? a

2. Multiplication and association law: When three numbers are multiplied, you can multiply the first two numbers and then the third number, or you can multiply the last two numbers and then the first number, and the product remains unchanged.

(a？ × ? b )× c？ = a？ × ? ( ? b？ × ? c)

These two multiplication laws are often used in combination.

Such as: 125×78×8.

3. Multiplication and distribution law: the sum of two numbers is multiplied by one number. You can multiply these two numbers with these two numbers first, and then add up the products. (a+b)×c=a×c+b×c

4. The nature of continuous division: one number divided by two numbers equals the product of these two numbers.

a \b \c？ = a ÷ ( b × c)

5. Simple calculation of expansion:

102×38-38×2 125×25×32 125×88 3.25+ 1.98 ? 10.32- 1.98 ? 37×96+37×3+37

Error-prone situation: 0.6+0.4-0.6+0.4? 38×99+99

(4) The meaning and nature of decimals:

Fractions with denominators of 1, 10, 100, 1000 ... can be expressed in decimals.

Decimal is another form of decimal.

3. Decimals are counted in tenths, hundredths and thousandths ... Write 0. 1, 0.0 1, 0.00 1 ...

4. The propulsion rate between every two adjacent counting units is 10.

5. Decimal reading and writing method: reading method: read the integer part according to the integer reading method, and the decimal part should read each number in order.

Writing: the integer part is written as an integer, and the integer part is 0, so write 0, and the decimal part writes each number in turn.

6. Properties of decimals: Add "0" or remove "0" at the end of decimals, and the size of decimals remains unchanged. Note: the "0" in the middle of the decimal cannot be removed, and some "0" at the end cannot be removed when approximating. Functions can be reduced to decimals, etc.

7. Decimal size comparison: compare the integer part first, the integer part is the same as the decimal part, and the decimal part is the same as the percentile. ...

8. Decimal size change law caused by decimal position movement:

Decimal point to the right: move one place, and the decimal point will be expanded to 10 times the original number;

Move two places, and the decimal will be expanded to 100 times of the original number;

Move three places, and the decimal will be expanded to 1000 times of the original number;

……

Decimal point moves to the left: move one place, and the decimal point is reduced by 10 times (the decimal point is reduced to the original number);

If you move two places, the decimal will be reduced by 100 times.

If you move three digits, the decimal number will be reduced by 1000 times (the decimal number will be reduced to the original number);

……

9. Rewrite the name number: 1 ton, 30kg+800g = (? ) tons

Length unit: km-m Decimeter? ———— ? centimetre

Area unit: square kilometer-hectare-square meter-square decimeter-square centimeter.

Mass unit: ton-kilogram-gram

10, find the approximate number of decimal places (rounding): (Keep the expression with two decimal places, with the accuracy of 1%)

Keep an integer, indicating accuracy to one place, one decimal place, indicating accuracy to ten places, and two decimal places, indicating accuracy to one hundred places. When taking an approximation, the 0 after the decimal point cannot be removed.

Rewriting large numbers. Rewrite first, then find the approximate number. Note: bring your unit.

(5) Triangle:

1. Definition of triangle: A figure surrounded by three line segments (the endpoints of every two adjacent line segments are connected or overlapped) is called a triangle.

Draw a vertical line from the vertex of the triangle to its opposite side. The line segment between the vertex and the vertical foot is called the height of the triangle, and the opposite side is called the bottom of the triangle. Key point: the drawing method of triangle height.

3. Characteristics of triangle: 1. Physical characteristics: stable. Such as: tripod for bicycles, tripod on telephone poles.

2. Characteristics of sides: the sum of any two sides is greater than the third side.

4, the classification of triangle:

By angle: acute triangle, right triangle, obtuse triangle.

Divided by side length: triangle with unequal sides and isosceles triangle (equilateral triangle or regular triangle is a special isosceles triangle).

The three sides of an equilateral triangle are equal and each angle is 60 degrees. (The concepts of top angle, bottom angle, waist and bottom)

5. The sum of the internal angles of the triangle is equal to 180 degrees. Calculation and format of degree.

6. Combination of graphics: Two identical triangles can definitely be combined into a parallelogram.

7. Dense shop: The patterns that can be densely laid are rectangle, square, triangle and regular hexagon.

(6) Addition and subtraction of decimals:

1、 ? Calculation rule: the same digit is aligned (decimal point is aligned), and the calculation is made according to the integer calculation method. The decimal point of the obtained number should be aligned with the decimal point on the horizontal line. The result is that decimals should be simplified according to the nature of decimals.

2、 ? Vertical calculation and check calculation. Pay attention to the horizontal answer, not the result of checking calculation.

3、 ? The four operation orders and algorithms of integers are also applicable to decimals. (Simplified calculation)

(7) Statistics:

Broken line statistical chart: a unit length is used to represent a certain quantity, points are drawn according to this quantity, and then the points are connected in turn by line segments.

Advantages: You can not only see the quantity, but also see the change of quantity, predict the future trend and provide guidance and help for future production and life.

(8) Mathematical wide angle: planting trees.

Number of intervals = total length ÷ interval length

Situation classification: 1, planting at both ends: number of plants = number of intervals+1.

2. Planting one head and not planting the other: number of plants = number of intervals.

3. No planting at both ends: number of plants = number of intervals-1.

4. Close: number of trees = number of intervals.