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If the rational number a is greater than the rational number B, then () A. The absolute value of a is greater than that of B B. The absolute value of a is less than that of B C. The opposite number of a is greater than that of B D. The opposite number of a is less than that of B
A. When a > 0 and B < 0, the absolute value of a is not necessarily greater than that of B, so this option is wrong;
B. When a > b > 0, the absolute value of a is greater than that of B, so this option is wrong;
C. Because a > b, the opposite number of a is less than the opposite number of B, so this option is wrong;
D. Because a > b, the opposite number of a is less than that of B, so this option is correct
Therefore, D
1. A class of teachers and students self-made teaching aids, a total of 144 pieces of mathematics and physics teaching aids, of which mathematics teaching aids is half of the physical teaching aids. How many pieces of mathematics and physics teaching aids are there? 2. Given that the circumference of a rectangle is 30 cm, the length is 3 cm more than the width 3. A patriotic health inspection working group has 30 members. According to the size of the task, it should be divided into three teams, so that the ratio of team a, B, C and 3 is 2:3:5, and the number of each team is calculated 4. Divide the 16 mu land into two parts and try to grow two new varieties of wheat. If the ratio of the area of the two parts is equal to 3:5, calculate the area of each part 5. A two digit number, ten digit number is twice of one digit number. If the ten digit number is exchanged with the one digit digit digit, the two digit number obtained is 36 smaller than the original number, so find the original number 6. A three digit number. The sum of the number in the tens and the number in the hundred is 15. The number in the hundred is 5 more than the number in the ten, and the number in the single digit is three times of the number in the ten digit 7. The sum of three consecutive even numbers is 10 times larger than the largest one. What is the sum of these three consecutive even numbers? 8. For a two digit number, the number in the tens is 3 less than the number in the digit. The sum of the number in the tens and the number in the digit is equal to one fourth of the two numbers. Find the two digits
Question 1
If there are x physics teaching aids, then x / 2 mathematics teaching aids
X+X/2=144
X = 96
So there are 48 mathematics teaching aids and 96 physics teaching aids
Question 2
If the length is x, then the width is x-3
(X+X-3)*2=30
The solution is x = 9
So the area is 9 * 6 = 54
Question 3
If there are 2x people in team a, 3x people in team B and 5x people in team C
2X+3X+5X=30
The solution is x = 3
So there are six in team a, nine in team B and fifteen in team C
Question 4
Suppose that part a has 3x mu, then part B has 5x mu
3X+5X=16
The solution is x = 2
So part a has 6 Mu and part B has 10 mu
Question 5
If the number of one digit is x, then the number of ten is 2x
(2X*10+X)-(X*10+2X)=36
The solution is x = 4
So the original number is 84
Question 6
Let the number of ten be x, then the number of one digit is 3x, and the number of hundred digit is x + 5
3X+X+(X+5)=15
The solution is x = 2
So the original number is 726
Question 7
If the even number in the middle is x, then the first even number is X-2 and the third even number is x + 2
(X-2) + x = 10, the solution is x = 6
To sum up, the sum of these three consecutive even numbers is equal to 18
Question 8
If the number of one digit is x, then the number of ten digits is x-3
X+X-3=[(X-3)*10+X]/4
The solution is x = 6
So the original number is 36
Answers to 8 questions on page 108
3, 9.2 coins
4, 320 yuan
5, 12
6, 2 hours, 70 kmh
7, [1] 45 pieces, [2] 35 pieces, [3] 55 pieces
8, 74 km h 94 km h 84 km h
9, [1] 84 years old [2] 38 years old [3] 80 years old
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Given | x-3 | + (a + 2) 2 = 0, find the value of the algebraic expression 1 / 3 (3ax? - ax + 3) - (ax? - 1 / 2ax-1) It is proved that the values of the algebraic formula 7a 3 - 6A 3 B + 3A 3 B + 3 + 3A 3 + 6A 3 B-3A A2 b-10a 3 - 7 are independent of the values of a and B
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In order to encourage energy conservation, a certain place has made the following provisions on the charging standards for residential users: if the monthly electricity consumption of each household does not exceed 100 kwh, a yuan will be charged per kwh; if it exceeds 100 kwh, then B yuan per kWh will be charged; if it is more than 200 kwh, a fee will be charged
First question:
As it does not exceed 100 degrees, the electricity charge payable is 75A
Second question
If it is more than 100 degrees, the electricity fee payable is 100A + (175-100) B = 100A + 75B
Third question
If the tariff payable is y, then
y=ax x≤100
100a+(x-100)b x>100
If it's more than 200 degrees, isn't it over?
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The monthly water consumption does not exceed 12 tons and the part exceeding 18 tons A portion of not more than 18 tons Charge standard (yuan / ton) 2.00 2.50 3.00 If the user pays 45 yuan for water in May, how many tons of water will the user use this month? There must be a formula On a parallel road beside the railway, there is a pedestrian and a cyclist traveling eastward at the same time. The pedestrian speed is 3.6 km / h, and the speed of cyclists is 10.8 km / h. a train comes from behind them. It takes 22 seconds to pass the pedestrian and 26 seconds to pass through the car. How long is the train body?
Design water x tons
2*12+6*2.5+3（x-18）=45
3（x-18）=6
x=20
Suppose the train speed is V and the pedestrian speed is 3.6km/h, i.e. 1m / s,
The speed of cyclists is 10.8 km / h, or 3 meters per second,
Then the equation (V-1) * 22 = (v-3) * 26,
V = 14m / S is obtained
The train length is (14-1) * 22 = 286m
A=1/3 X=-3
1. Subtract - 3x to get the second power of X. The formula - 3x + 6 is———————— 2. The quotient of (the fourth power of a - the fourth power of B) divided by (the second power of a - the second power of B) is—————— 3. (- -) (- 4a to the 2nd power) = 12a to the 4th power - 12a to the 3rd power + 4a to the 2nd power 4. If a (half + x) (negative half-x) = the fourth power of x-76, then a=————
-3x + (x? - 3x + 6) = x? - 6x + 6 the answer is x? - 6x + 6 (a ^ 4-b ^ 4) / (a? B?) = (a? + B?) (a? - B?) / (a? - B?) = (a? + B?) = (12a ^ 4-12a ^ 3 + 4A?)
1. Calculation: (1) the power · n of 211 × 555 + 445 × 789 + 555 × 789 + 211 × 445 (2) s = 1-2 + 3-4 +... + (- 1) n + 1 2. Xiao Ming went to his father's supermarket to participate in social practice activities. One day, Xiao Ming came back with his father's 58 pieces of 200 change notes from the bank for customers to change when they paid. After careful cleaning up, Xiao Ming found that there were 20 pieces with a face value of 1 yuan, 7 pieces with a face value of 10 yuan, and all the rest were 2 yuan and 5 yuan notes. Please calculate how many 2 yuan and 5 yuan banknotes are there
(1) from 211 × 555 + 445 × 789 + 555 × 789 + 211 × 445 = 211 × (555 + 445) + 789 × (445 + 555) = 211000 + 789000 = (211 + 789) × 1000 = 1000000. (2) from 1-2 + 3-4 +. + (- 1) ^ (n + 1) · n
First grade math problem, find the answer If a supermarket wants to buy a computer, the market price of this model of computer is 5600 yuan per set. At present, two computer suppliers, a and B, are bidding for computers. If a computer supplier proposes to purchase more than ten computers, it will be charged with a 20% discount from the 11th one; if B computer supplier wants to buy more than 10 computers, it will be priced at a 10% discount. Which one should be chosen?
A:
Set the number of units purchased as X
At X11:
The price of a is 5600 × 10 + 0.8 × 5600 (X-10) = 4480x + 11200
The price of B is g (x) = 0.9 × 560x = 5040x
Let g (x)
1. In paper cutting, if the paper used has been folded in half n times (n ≥ 1 and N is an integer), then the cut-out pattern has at least Axis of symmetry 2. In line segment, angle, isosceles triangle, parallelogram and circle, it must be axisymmetric and centrosymmetric 3. When two athletes a and B looked in the mirror, Xiao Ming saw that their chest numbers in the mirror were and, Then the number on the chest of a is, and the number on the chest of B is 4. As shown in the figure, △ ABC, ab = AC, D and E are on AC and ab respectively, and De is vertical If AB + BC = 10 cm, the circumference of △ DBC is cm 5. The five pointed star pattern on the national flag can rotate around its center at least to coincide with itself 6. As shown in the figure, it is known that in RT △ ABC, ∠ C = 90 ° and points D, e and F are located in AB, AC, and F, respectively On BC, the quadrilateral cfde is a square. If ad = 3, BD = 4, then the shadow in the figure The area of the part is 7. As shown in the figure, divide the diagonal AC of the square ABCD with side length of 1 into n segments Make a square for a diagonal line. The sum of the circumference of all small squares is 8. As shown in the figure, in the rectangle ABCD, ab = 4cm, BC = 2cm, with a as the center If ad is the intersection point of the circle made by radius and Ba extension line, then The area is cm2
There are so many topics, and some of them are incomplete
1. At least 2
2. Line segment and circle
5.72°
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