The circumference of a circle is 12.56 cm. If the diameter is increased by 1 / 4, how much is the area increased?

The circumference of a circle is 12.56 cm. If the diameter is increased by 1 / 4, how much is the area increased?

The diameter of the circle increased: 12.56cm ／ 3.14 × 1.25 = 4cm × 1.25 = 5cm, the area increased: (4cm ／ 2) & # 178; × 3.14 ／ [(5cm) & # 178; × 3.14] = 4cm & # 178; × 3.14 ／ [25cm & # 178; × 3.14] = 4 / 25 (Times) increased: [(5 & # 178; - 4 & # 178;) CM & # 178;]

If you draw a circle arbitrarily and increase its diameter by 1 / 3, then the area of the circle now is the original (). If you draw a circle arbitrarily and increase its circumference by 1 / 3, you can find that the area of the circle is the same

The diameter is D, and the area of the original circle is a = Π * (D / 2) square
After transformation, the area of the circle is the square of B = Π * ((4 / 3) d / 2)
So, B: a = (4 / 3) square: 1
The answer is 16 / 9 times the original

If you draw a circle arbitrarily and increase its radius by one third, what is the ratio of the area of the circle to that of the original circle

Pie times the square of four-thirds R: pie's Square
16：9

There are 100 students in class 61 and class 62. One third of class 61 is equal to one half of class 62,
For two barrels of oil, the first barrel is 18 kg more than the second barrel. After pouring 7 kg from the second barrel, the mass ratio of oil in the second barrel to the first barrel is 4:9. How many kg are there in each barrel/

If there are x people in class 61, then there are (100-x) people in class 62. According to the equation (1 / 3) x = (1 / 2) (100-x) 2x = 3 (100-x) 2x = 300-3x 2x + 3x = 300, 5x = 300 x = 60, there are 60 people in class 61 and 40 people in class 62

There are 86 students in the two classes, four times the number of students in class one and six times the number of students in class two. There are 432 students in total. How many students in class two and class one?

Class X, Class Y
4X+6Y=432
X+Y=86
Solve the equation by yourself

After 1 / 8 of class one is transferred to class two, the two classes are equal. The ratio of class one to class two is (): ()

4：3

1. Transfer one fifth of the number of people in class one to class two, which means that the number of people in class two is equal. The original ratio of the number of people in class one to class two is ()
2. On the map of scale 1:5000000, the distance between city a and city B is 10cm, The actual distance between the two cities is (). 3. The following is the donation situation of boys and girls in grade five. Boys: 5, 9, 10, 8, 15, 10, 20, 11, 10, 15, 10, 15, 12, 13, 8, 7, 6, 18, 15. Girls: 7, 9, 10, 11, 3, 5, 2, 4, 8, 6, 13, 17, 30, 12, 16, 15, 14, 18. What are the median and mode of boys and girls? 5, The ratio of the bottom radius of the cylinder and the cone is 1:2, and the height of the cylinder is the height of the cone

If the first question is to fill in the blanks, it can be done in this way simply. If the number of people in a class is one fifth, then the number of people in a class must be a multiple of five. Suppose the number of people in a class is five, adjust one fifth, that is, adjust 5 * 1|5 = one, and if the number of people in two classes is equal, it will be four, The number of students in class 2 was 3, so the original ratio was 5:3! The second question was 10 * 50000000 = 50000000cm, the third question arranged the number of students from small to large, the middle number was the median, the mode was 15, the fourth question was s = Pai * r * r, the radius ratio was 1:2, the bottom area ratio was 1:4, the volume formula was v = s bottom * h, for the cone v = s bottom * h * 1 / 3, the volume of the cylinder was equal to the cone, then H1: h2 = 4:3

In two classes, 15 / 2 of the number of students in one class is transferred to two classes. At this time, the number of students in two classes is 4 / 3 of the number of students in one class. How much of the number of students in one class is the number of students in the whole grade?

15 / 2 of the first class is transferred to the second class
Then there are 1-2 / 15 = 13 / 15 left in class one
At this time, the number of class 2 is 4 / 3 of that of class 1
So class 2 has (13 / 15) * (3 / 4) = 13 / 20
So the whole grade has 13 / 15 + 13 / 20 = 91 / 60
So the original number of class 1 is 1 / (91 / 60) = 60 / 91 of the total number of students in the whole grade

There are two classes in grade five. Transfer 215 of class one to class two. At this time, 35 of class two is 34 of class one. How much of class one is the number of the whole grade?

The ratio of class two to class one is 34:35 = 5:4, 45 + 4 ^ (1-215), = 49 ^ 1315, = 2039; a: the original number of class one is 2039

The number of students in class one of grade five is five sixth of that in class two of grade five, and class one of grade five accounts for half of the total number of students in the two classes
What fraction?

1/(5/6)=6/5=1.2
5/6/(1+5/6)+5/11