There are some books on Xiaoming's bookshelf. The number of books ranges from 100 to 150. Among them, 15 are story books, 17 are science and technology books, and most of them are on the bookshelf______ This is a book

There are some books on Xiaoming's bookshelf. The number of books ranges from 100 to 150. Among them, 15 are story books, 17 are science and technology books, and most of them are on the bookshelf______ This is a book

According to the meaning of the title, the number of books can be divided not only by 5, but also by 7 10, 4 × 35 = 140. A: there are 140 books on the shelf at most

The number of books on the shelf ranges from 110 to 150, of which 1 / 5 are science and technology books and 1 / 7 are story books. How many books are there on the shelf?
Supplement: a train is 250 meters long. It passes through a bridge at the speed of 72 kilometers per hour. It takes two minutes from the front of the train to the rear of the train to leave the bridge. How long is the bridge?

1. The number of books on the shelf is between 110 and 150, of which 1 / 5 are science and technology books and 1 / 7 are story books. How many books are there on the shelf?
The common multiple of 5 and 7 is between 110 and 150, only 140
2. A train is 250 meters long. It passes through a bridge at the speed of 72 kilometers per hour. It takes two minutes from the front of the train to the rear of the train to leave the bridge. How long is the bridge?
72 km / h = 20 m / s, 2 min = 120 s, if the bridge length is l m, then
L+250=20*120
L = 20 * 120-250 = 2150 (m)

There are less than 200 books on the shelves of class 63, of which one sixth are story books and one seventh are science and technology books,
There are at most () books on the shelf

According to the meaning of the title
We can know that the number of books can be divided by 6 and 7, that is, the number is a multiple of 6 × 7 = 42
200/42=4…… 32 (remainder)
So there are at most 200-32 = 168 books or 42 × 4 = 168 books on the shelf

3x+2＞2x-2 8x-2≤7x+3 3（x-1）＜2（x+9） 2（4x+3）≤3（2x+5） 5x-3≥2x 2（x+2）≤x+3
Solving inequality
3x+2＞2x-2
8x-2≤7x+3
3（x-1）＜2（x+9）
2（4x+3）≤3（2x+5）
5x-3≥2x
2（x+2）≤x+3

x>4
x≤5
x

1 + 2 * 3 + 4 * 5 + 6 * 7 + 8 * 9, fill in the brackets and make the answer equal to 505

(1+2*3+4)*5+(6*7+8)*9=505

3y=7-2x 3x=7+5y
3y=7-2x
3x=7+5y
Quadratic equation with two variables

y=7/3-2/3*x
Substituting 3x = 7 + 5Y
We get 3x = 7 + 35 / 3-10 / 3x
19/3x=56/3
x=56/19
y=41/57

Simplification ratio (Mathematics): 32:48 12 / 7:24 / 5 12:5 / 424:72 1.6:6.47 / 2:5 / 3

Jane's ratio (Mathematics)
32:48=2:3
12/7:24/5=1/7:2/5=5:14
12:5/4=48:5
24:72=1:3
1.6:6.4=1:4
7/2:5/3=21:10

It is known that the symmetry axis of parabola is a straight line x = 1, and through (1,2) and (- 2,5), the relation of quadratic function is obtained

If the axis of symmetry is a straight line x = 1 and passes through (1,2), then
The vertex coordinates are (1,2), so
Let the relation of this quadratic function be y = a (x-1) &# 178; + 2
After (- 2,5), then
5=a(-2-1)²+2
9a=3
a=1/3
So the relation of this quadratic function is y = 1 / 3 (x-1) &# 178; + 2

What is the product of 10 and the quotient of 3.5 divided by 0.7 and multiplied by 0.2?

Hello
（10+3.5÷0.7）×0.2
=（10+5）×0.2
=15×0.2
=3

Set a = {x 2x + 1

A ∩ B = {X - 3}