5M? + 12M? +23M? =(50×40)x
200x =40M?
x = 40÷ 200
= 0.2 m
Answer: It can be 0.2M thick.
Analysis: Cement, stone and sand are a volume. Paving such a large volume of road. The surface area of the playground is 50*40. Divide the total volume by the surface area to get the height. Namely the thickness of the road. (Volume = length * width * height)
Question 2: Setting: After X days, the rice will be finished.
2*( 15X)=20X+80
30X=20X+80
10X=80
X=8 days
Weight of rice: 15 * 8 = 120kg.
Weight of flour: 2 * 120-240kg.
A: Yes. . . .
Analysis: Eat 15 kg of rice every day for ***x days. So the total weight of rice is 15*x kg. Eat 20 kilograms of flour every day for ***x days, and there are 80 kilograms left. So the total amount of flour is 20*x+80 kg. And because the weight of flour is twice that of rice. So the equation is listed: 2*( 15X)=20X+80.
This is the step and process to solve the problem. Hope to adopt ~ ~ ~