Excuse me, how to get the mathematical understanding of exercise 5.7 (186 pages) in the mathematics book of the first volume of the seventh grade? The diameter of two cylindrical containers is 4cm and 8cm respectively, and the height is 39cm and 10cm respectively. We first fill the second container with water, and then pour it into the first container. Q: after pouring, how many centimeters is the water surface in the first container from the bottle mouth? Xiao Ming did this: let the water surface in the first container be x cm away from the bottle mouth after pouring. The equation Π· 2 & sup2; (39-x) = Π· 4 & sup2; · 10 was solved, and x = - 1 Can you give a reasonable explanation for his result? Another topic: A bookshelf is 88cm wide, and a certain volume is full of the first volume of mathematics books and Chinese books, a total of 90. Xiaoming measured that a mathematics book is 0.8cm thick, and a Chinese book is 1.2cm thick. Do you know how many mathematics books and Chinese books are on this bookshelf?

Excuse me, how to get the mathematical understanding of exercise 5.7 (186 pages) in the mathematics book of the first volume of the seventh grade? The diameter of two cylindrical containers is 4cm and 8cm respectively, and the height is 39cm and 10cm respectively. We first fill the second container with water, and then pour it into the first container. Q: after pouring, how many centimeters is the water surface in the first container from the bottle mouth? Xiao Ming did this: let the water surface in the first container be x cm away from the bottle mouth after pouring. The equation Π· 2 & sup2; (39-x) = Π· 4 & sup2; · 10 was solved, and x = - 1 Can you give a reasonable explanation for his result? Another topic: A bookshelf is 88cm wide, and a certain volume is full of the first volume of mathematics books and Chinese books, a total of 90. Xiaoming measured that a mathematics book is 0.8cm thick, and a Chinese book is 1.2cm thick. Do you know how many mathematics books and Chinese books are on this bookshelf?

There are 50 math books and 40 Chinese books
Set: mathematics book as X, Chinese book as y
x+y=90
0.8x+1.2y=88
The solution is x = 50... Y = 40