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Equations solve practical problems about fractions 1. The number of science and technology books in the library is equivalent to 5 / 12 of story books [1] If there are 360 storybooks, how many are there 【2】 If there are 150 science and technology books, how many story books are there? Xiao Ming read a quarter of the book, and the next day he began to read it from page 25. How many pages is the book? Using equation
[1] 360 × 5 / 12 = 150 (copies) or X books of science and technology
[2] 150 △ 5 / 12 = 360 (copies) or X story books x × 5 / 12 = 150 x = 360
Suppose the book has x pages
1/4x=14
x=56
A: the book has 56 pages
In order to solve practical problems, we should pay attention to the following problems
(1) The units should be unified;
(2) Be careful when setting unknowns_____________ ；
(3) Pay attention to the rationality of solution___________ .
(1) The units should be unified;
(2) Be careful when setting unknowns_ Equivalency relationship;
(3) To get a reasonable solution, we should pay attention to moving items and removing brackets
Set up equations to solve the following practical problems
(1) The leopard said, "my speed is 110 kilometers per hour." the elephant said, "its speed is 30 kilometers more than twice my speed." how many kilometers per hour can the elephant reach at the fastest?
The leopard's speed is 30 kilometers more than twice that of the elephant
Leopard's speed - 30km = twice that of elephant
Let the speed of an elephant be X
110-30=2x
X = 40 km / h
The process of solving practical problems with equations or equations can be summarized as?
It should be solving the equation
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- 6. Practical problems of Grade 7 (solved by equation) 1. Ask the child's age, and answer: "9% less than half of my father's age", ask the father's age, and answer: "3 times older than my child's age", and ask the child's age? 2. The price of a commodity is increased by 50% of the cost price, and then 20% off (80% of the price). The price is 240 yuan. How much is the profit of this commodity? 3. There is a train passing through the first and second tunnels at the speed of 600 meters per minute. It is known that it takes 5 seconds more to pass through the second tunnel than the first tunnel. The length of the second tunnel is twice that of the first tunnel, and it is 50 meters shorter. What is the length of each tunnel? (write steps or equations)
- 7. Two 7-year-old practical problems (solved by equation) 1. Xiaoming and Xiaoli run back to each other along the circular track at the same time. They meet each other every 15 seconds. It is known that Xiaoming runs a lap for 24 seconds, and Xiaoli runs a lap for how many seconds? 2. At present, the concentration of 5% Guozhen beverage is 200g. If the concentration is to be increased to 10%, how much Guozhen should be added to the beverage?
- 8. Three times of X is more than 18
- 9. 10 is less than 4 times of x 2. How to set up the equation and what is the solution of X
- 10. The sum of a number and 3 is 10 less than twice the number?
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- 17. Solve the equation 5x + 18 = 3x + 44 15x-1.4 * 5 = 5x + (107-2.2) Tonight,
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- 19. When k is what value, the solution of equation (5x-6x) △ 8 = K / 2 + 1 is nonnegative?
- 20. 1 x + y = k, X-Y = 20 (x, y are positive numbers) find the value of K 2, the solution of the equation 5x + 12 = 4A about X is negative, then the value range of a is? 1 Question 1 x + y = k, X-Y = 20 (x, y are positive numbers) to find the value of K In question 2, if the solution of the equation 5x + 12 = 4A of X is negative, then the value range of a?