There is a barrel of oil. The sum of oil and barrel is 49 kg. After using 40% of the oil, the sum of oil and barrel is () kg

With 40% deoiling, the total mass sum should also be reduced by 40%. 49 (1-40%) = 29.4

It's necessary to calculate formula and analyze thinking
A cube billet with 20 cm edge length is forged into a cuboid steel with 16 square cm bottom area. How long is the cuboid steel
Pay attention to the unit

The volume of the steel has not changed, only the shape has changed
So: volume = length x width x height
20x20x20 = 16x long
Calculated: length = 500 cm
1 decimeter = 10 cm
So 500 cm = 50 decimeters
So the length of steel is 50 decimeters

Take off formula calculation. 51.8-4.8 × (2.03-0.18) 12-1.25 × 635.4 × 0.29-0.29 × 25.4 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 48 × 0.69 + 3.1 × 4.8

（1）51.8-4.8×（2.03-0.18），=51.8-4.8×1.85，=51.8-8.88，=42.92；（2）12-1.25×6，=12-7.5，=4.5；（3）35.4×0.29-0.29×25.4，=（35.4-25.4）×0.29，=10×0.29，=2.9；（4）48×0.69+3.1×4.8，=4.8×6.9+3.1×4.8，=（6.9+3.1）×4.8，=10×4.8，=48．

1. Including circle, quadratic function, trigonometric function, equation, etc
2. The more sets, the better
3. The questions should be classic
four

If the price of a drug is reduced by 20% at first, and then by 20% after the price reduction, the current price is a few% of that before the price reduction

100%*（1-20%）*（1-20%）=64%

Let f (x) > or = 2F (x) be constant if f (x + T) > or = 2F (x) is defined in the domain [T, t + 2]?
The function f (x) is an odd function on R. when ＞ or = 0, there is an analytic formula F (x) = the square of X. now let X be in the domain of definition [T, t + 2], so that f (x + T) > or = 2F (x) is constant, and find the value range of T?

When t > = 0
[T, t + 2] is a positive interval
F(X+T)>=2F(X)
=>(X+T)^2>=2X^2
(X-T)^2-2T^2=√2
When t

The problem of "algorithm and program block diagram" in high school mathematics
We have a problem
INPUT X
X=YOUR NAME
PRINT X
END
What is the output x? My classmate said that he wanted to write his own name. Is that right?

Output your name

The price of a color TV set is 1944 yuan after two successive price cuts of 10%______ Yuan

Suppose that the original price of each color TV set is x yuan. According to the equation, X × (1-10%) × (1-10%) = 1944, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 0.81x = 1944, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; and; &A: this kind of color TV set used to cost 2400 yuan per set

What is the leap year in 1900, 1998, 2000, 2008, 2010, 2012 and 2020?

Answer: 2000, 2008, 2012 and 2020 are leap years

1. There is a column number - 1 / 2,2 / 5, - 3 / 10,4 / 17 Then the seventh number is_ The nth number is .
2. Observe the following components: - B / A, 2b / a and#178;, - 3B / a and#179;, 4b / A ^ 4 The 10th fraction is_ The nth fraction is________ .

(molecule n) / (the square of molecule n plus 1) * - the nth power of 1), and so on
(- 1 to the nth power) * n * B / (a to the nth power)
*Multiply / divide

There is a barrel of oil. The sum of oil and barrel is 49 kg. After using 40% of the oil, the sum of oil and barrel is () kg