Sixth grade math graphics with answers 40 (with map) urgent! Hurry up! It's better to be simple

Sixth grade math graphics with answers 40 (with map) urgent! Hurry up! It's better to be simple

Concept:
The formula for calculating the circumference of a circle: circumference × diameter
The formula for calculating the area of a circle: the second power of circumference × radius
The method of calculating the ring: calculate the outer circle, calculate the inner circle, subtract the inner circle from the outer circle
PI ≡ 3.141596253
Generally, the PI is 3.14
Here is the power of 1-20:
The second power of 1: 1
The second power of 2: 4
The second power of 3 is 6
The second power of 4 is 16
The second power of 5 is 25
The second power of 6 is 36
The second power of 7 is 49
The second power of 8 is 64
The second power of 9 is 81
The second power of 10 is 100
The second power of 11 is 121
The second power of 12 is 144
The second power of 13 is 169
The power of 14 is 196
The second power of 15 is 225
The power of 16 is 256
The second power of 17 is 289
The second power of 18 is 324
The second power of 19 is 361
The second power of 20 is 400
If you can recite the quadratic power of 1-20,
That's very helpful for calculation, such as calculating the area of a circle
(it's engraved word by word by myself. I hope you can get something!)
In example 1, calculate the perimeter and area of the following figures: (unit: cm)
Solution to the circumference of rectangle: (4 + 3) × 2 = 14 (CM)
Rectangular area: 4 × 3 = 12 (square centimeter)
Square perimeter: 3 × 4 = 12 (CM)
Square area: 3 × 3 = 9 (square centimeter)
[key to problem solving and tips]
Memorize and correctly use the formula of length, square perimeter and area, pay attention to the difference between perimeter and area unit
In example 2, calculate the area of the following figures: (unit: meter)
Area of solution parallelogram: 20 × 16 = 320 (M2)
Triangle area: 15 × 6 △ 2 = 45 (M2)
Trapezoid area: (20 + 28) × 10 △ 2 = 240 (M2)
[key to problem solving and tips]
Memorize the area formula of parallelogram, triangle and trapezoid, and use it correctly
(unit: decimeter)
Circumference: 2 × 3.14 × 3 = 18.84 (decimeter)
Area: 3.14 × 32 = 28.26 (square decimeter)
Circumference: 3.14 × 10 = 31.4 (decimeter)
[key to problem solving and tips]
Memorize the formula of circumference and area, distinguish diameter and radius, and pay attention to the difference between circumference and area
[key to problem solving and tips]
Example 5 the area of the parallelogram in the figure below is 12 square centimeters. Find the area of the triangle with diagonal line
Solution 12 △ 2 = 6 (square centimeter)
[key to problem solving and tips]
The area of a triangle is equal to half the area of a parallelogram of equal height and equal base
Which triangle in the figure below has the same area as the one with the diagonal line drawn? What's its area? Can you draw a triangle with the same area as the one with the diagonal line drawn?
The area of solution triangle abd and triangle CBD is equal to the area of triangle with diagonal line
3 × 2 △ 2 = 3 (square centimeter)
Example 7 calculate the area of the shadow part of the figure below. (unit: cm)
The solution is 4 × 4-3.14 × 4 × 4 △ 4.2 × 2 × 3.14 △ 2
＝16－12.56＝4×3.14÷2
= 3.44 (cm2) = 6.28 (cm2)
[key to problem solving and tips]
The area of the building
(2) The area of the shadow is exactly half the area of a circle with a radius of 2 cm
In example 8, the circumference of the circle in the figure below is 18.84 cm
Solution 18.84 △ 3.14 △ 2 = 3 (CM)
＝13.5－7.065
= 6.435 (cm2)
[key to problem solving and tips]
The radius of a circle (also the top and bottom of a trapezoid)
Example 9 the figure below is a circular ring, r = 2 cm, r = 1 cm
＝3.14×3
= 9.42 (M2)
Cm)
[key to problem solving and tips]
Circle area = big circle area - small circle area
Calculate the area of shadow in case 10. (unit: cm)
Solution (16 △ 2) × 4 △ 2 × 2 = 32 (square centimeter)
[key to problem solving and tips]
Turn the shadow to:
It only needs two triangle areas with bottom (16 △ 2) and height 4