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Use the rounding method to find the approximate value of 30951 (accurate to hundreds), what is the result
thirty-one thousand
A 470 meter long train passes the 1030 meter long bridge in 1 minute and 20 seconds, and then passes a tunnel in 40 seconds at the same speed. How long is the tunnel?
1 minute 20 seconds = 80 seconds, [(470 + 1030) △ 80] × 40-470 = 18.75 × 40-470 = 750-470 = 280 meters; answer: the tunnel is 280 meters long
Divide a circle into several equal parts and put it together into a rectangle. The length of the rectangle is 6.28cm. Calculate the area of the circle
If you remember correctly, the length of a rectangle is 6.28, and the width is the radius of a circle. According to calculus, the area of a rectangle should be the same as that of a circle! So the radius of a circle is obtained. The square of the radius is 6.28, and the area of a circle is 6.28 × 6.28 / Π
The reason is ha. When I was a child, my teacher taught us the area of a circle. He took a circle divided into 10 parts and put it together into a rectangle. We measured its length and width and got the area of the rectangle and the "circle". The rectangle was obtained by putting together a few sectors cut from the center of the circle to form an approximate rectangle whose width is the radius of the circle, So the area may not change. So that's it
This is my initial guess, I don't know if it's right!
What is the negative fifth power of one fifth?
(1/5)^(-5)=1/[(1/5)^5]=1/[1/(5^5)]=5^5=3125
Telecom companies have introduced two charging methods for mobile phones. Charging method a is 50 yuan per month. In addition, charging method B is 0.6 yuan per minute for communication time, and charging method a is 0.4 yuan per minute for call time. Charging method B is 0.6 yuan per minute for communication time?
If the monthly consumption of the user is 360 * 0.60 = 216 yuan and the monthly rent is 216-50 = 166 yuan and 0.4 yuan per minute, the total consumption is 166 / 0.4 = 415 minutes,
As shown in the figure, in the known trapezoidal ABCD, ad ∥ BC, AD + BC = DC, M is the midpoint of AB, prove: DM ⊥ MC
If Mn is parallel to AB and CD is parallel to N, then DN = CN and Mn = 1 / 2 (AD + BC) = 1 / 2CD
So there is Mn = DN = CN. According to the characteristic (equilateral equal angle) of isosceles triangle and the theorem of the sum of internal angles of triangle, we can prove the problem of ∠ DMC = 90
The mass of the following objects closest to 50g is ()
A. An egg B. a ninth grade physics textbook c. a desk D. a hen
One kilo is 500g, one or two is 50g. An egg is about one or two, that is 50g. So a is correct; the physics textbook is about 0.25kg; the desk is about 25kg; a hen is about 2kg
Xiao Ming, Wang Qiang and Gu Hai took a taxi together and agreed to divide the fare according to the length of the journey
Xiao Ming, Wang Qiang and Gu Hai took a taxi together, and agreed to divide the fare according to the distance. Xiao Ming got off at a quarter of the whole journey, and Wang Qiang got off at three fifths of the whole journey. Only Gu Hai got to the destination, and Gu Hai paid 37 yuan. How much should Gu Hai bear? How much should Xiao Ming and Wang Qiang pay Gu Hai?
1/4X+3/5X+X=37
(1/4+3/5+1)X=37
X=20
Gu Hai should pay 20 yuan, Xiao Ming 5 yuan and Wang Qiang 12 yuan
As shown in the figure, Xiao Hong cuts a 4 cm wide strip from a square, and then cuts a 5 cm wide strip from the remaining rectangular paper along the direction parallel to the short side. If the area of the strips cut twice is exactly the same, what is the area of each strip? What is the area of the original square?
Suppose the side length of the square is xcm, then according to the meaning of the question: 4x = 5 (x-4), the solution is: x = 20. Then 4x = 80 (cm2), 20 × 20 = 400 (cm2). Answer: the area of each strip is 80cm2, the area of the original square is 400cm2
In triangle ABC, angle A: angle B: angle c = 2:3:7, angle c=
In the triangle ABC, angle A: angle B: angle c = 2:3:7,
Angle c = 180 × 7 ^ (2 + 3 + 7)
=105°；
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