Perimeter of plane figure

1, the perimeter of the rectangle = (length+width) ×2, and C=(a+b)×2.

2. The circumference of a square = side length ×4, and C=4a.

3. Diameter = radius ×2, d = 2r, radius = diameter ÷2, r=d÷2.

4. The circumference of a circle = pi× diameter = pi× radius× 2, and c = π d = 2π r.

Plane graphic area

1, rectangular area = length× width, S=ab.

2. Area of a square = side length × side length, S=a×a=a?

3. The area of triangle = base × height ÷2, and S=ah÷2.

4. The area of parallelogram = base × height, and S=ah.

5. Trapezoidal area = (upper bottom+lower bottom) × height ÷2, S=(a+b)h÷2.

6. The area of a circle = pi × radius× radius, and S=πr?

7. The surface area of a cuboid = (length× width+length× height+width× height )× 2 = (AB+AH+BH )× 2.

8. Surface area of cube = side length × side length× 6, S=6a?

9. lateral area of cylinder = perimeter of bottom circle × height, S=ch.

10, cylinder surface area = top and bottom area+side area, S=2πr? +2πrh

Volume of three-dimensional graphics

1, cuboid volume = length× width× height, V=abh.

2. The volume of the cube = side length × side length× side length, V=a×a×a=a?

3. Volume of cylinder = bottom area × height, V=Sh, V=πr? h

4. The volume of the cone = bottom area × height ÷3, V=Sh÷3=πr? H3

Specific situational problems

Sum, difference and multiplication: (sum+difference) ÷2= large number, (sum difference) ÷2= decimal number.

Sum ÷ (multiple+1) = decimal, decimal × multiple = large number (or sum-decimal = large number).

Difference ÷ (multiple-1)= decimal, decimal × multiple = large number (or decimal+difference = large number)

Time unit conversion

1 century = 100 year, 1 year =65438+ February;

The big month (3 1 day) is 65438+August, and the small month (30 days) is April;

February 28th in a normal year, February 29th in a leap year, 365 days in a normal year and 366 days in a leap year;

1 day =24 hours, 1 hour =60 minutes, 1 minute =60 seconds, 1 hour =3600 seconds.