The radius of a circle is reduced by 1 / 10, and the area is reduced by several parts

The radius of a circle is reduced by 1 / 10, and the area is reduced by several parts

Area is equal to the ratio of circumference times the square of radius. From the radius of a circle reduced by 1 / 10, we can know that the radius is only 9 / 10 of the original, so the area is only 81 / 100 of the original, so we can know that the area is reduced by 19 / 100

When the radius of the cylinder increases by 10%, the circumference increases______ %And the area increased______ %．

[2 π (1 + 10%) R-2 π R] / 2 π r = [2 π 110% R-2 π R] / 2 π r = 20% π R / 2 π r = 10%. [π [(1 + 10%) R] 2 - π R2] / π R2 = [π 121% R2 - π R2] / π R2 = 21% π R2 / π R2 = 21%

The radius of a circle is 2 cm. If the radius is increased by 1 / 2, what is its area? What is its area?

The radius of a circle is 2 cm. If the radius is increased by 1 / 2, what is its area? What is its area?
The radius is increased by 1 / 2, and its area is:
3.14×【2×（1+1/2）】²
=3.14×3²
=3.14×9
=28.26
Its area is the original:
(1 + 1 / 2) × (1 + 1 / 2) = 1.5 × 1.5 = 2.25 times

The average score of one class is 96, the average score of the other class is 94, and the total average score is 95.04

Let X / Y 96x + 94y = 95.04 (x + y) x / y = 13 / 12

There are 52 students in class 51 and 48 students in class 52. The average score of the two classes is 90 points. The average score of class 2 is 5 points higher than that of class 1. What is the average score of the two classes?

If the average score of class one is x, then the average score of class two is (x + 5), then
52x+48(x+5)=90*(52+48)
100x+240=9000
100x=8760
x=87.6
The average score of class one is 87.6, and that of class two is 92.6

In the final exam, the average score of class A is 97, and that of class B is 95. The total average score of these two classes is 96.04. What is the ratio of class A to class B?
There should be a formula

If the number of class A is x and the number of class B is y, then 97x + 95y = 96.04 * (x + y), that is, 0.96x = 1.04y, then x: y = 1.04:0.96 = 13:12, so the number ratio of two classes is 13:12

There are 48 students in class 5 (1) and 52 students in class 5 (2). The average score of all the students in the two classes is 88. The average score of class 5 1 is 5 points higher than that of class 5 2
What is the average score of the two classes?

If the average score of class 52 is x, the average score of class 51 is (x + 5)
52x+48（x+5）=88×（48+52）
100x+240=8800
100x=8560
x=85.6
The average score of class 52 is 85.6,
The average score of class 51 is 85.6 + 5 = 90.6
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The students in class two are divided into groups for spring outing. The number of students in class one is equal. The number of students in class two is divided into 4 groups on average. The number of students in class two is divided into 6 groups on average
How many people are there in the two classes?
Formula

If there are two classes with X people in each group, there will be one class with x + 4 people in each group
4 (x + 4) = 6x
The solution is x = 8, so there are 48 people in each class and 96 people in two classes

There are 48 people in class 51 and 42 people in class 52. Each class is required to participate in tree planting activities in groups, so that the number of people in each group of the two classes must be the same, and the number of people in each group must be the largest
How many groups are they divided into?

The greatest common divisor of group 15, 48 and 42 is 6. Class 1 48 = 6 people / group * 8 groups, class 2 42 = 6 people / group * 7 groups, so there are 7 + 8 = 15 groups

There are 32 students in class 51 and 40 students in class 52. In order to make the number of each group equal, how many students are there in each group? How many students are there in each group
How many groups are they divided into

The greatest common factor of 32 and 40 is 8
32/8=4
40/8=5