There are 11 students borrowing books from the book corner. To ensure that at least one student can borrow three books, how many books should there be at least in this book corner?

11 × 2 + 1 = 23 (Books), a: there are at least 23 books in this book corner

The school library has bought some new books for students. If they borrow 8 books in each class, there are 18 left. If 10 of them borrow 7 books in each class,
How many classes are there in the school? How many books have the library bought?

There are x classes in the school,
8x+18=70+7(x-10)

What is the difference between - 3 / 7 and - 1

-1 + (- 3 / 7) = = - 1 and 3 / 7

Honghong and Liangliang planted a small tree with a trunk diameter of 5 cm and a height of 1.5 m. after the survival of the small tree, it can grow 10 cm in height and 3 cm in trunk diameter every year
(1) How many cubic meters of timber will be finished in five years?
(2) How many cubic meters is the volume of the biggest square wood made from this log?

After 5 years, the height of the small tree is 150 + 50 = 200 cm = 2 m, the diameter of the trunk is 15 + 5 = 20 cm = 0.2 m, and ∵ v = π R & # 178; × h ∵ v = 0.1 × 0.1 × 2 × π = 0.02 π m3 (2) ∵ the log should be processed into the largest square timber

Three fourths of a number is 90. What's five sixths of a number?

Three fourths of a number is 90
That means the number is zero
90÷3/4=120
Five sixths of the number
120×5/6=100

For the rational number AB, define the operation "" as follows: a b = a + B, find the values of 2 * 3 and (- 3) * - 4
For the rational number AB, define the operation "" as follows: a b = AB / A + B, find the values of 2 * 3 and (- 3) * - 4

2*3=6/2+3=6/5
(-3)*(-4)=12/（-3）+（-4）=-12/7

There are 40 more pear trees than apple trees in the orchard, 1.2 times as many as apple trees. How many pear trees are there?

40 △ 1.2-1 = 40 △ 0.2 = 200; 200 + 40 = 240; answer: 240 pear trees

If A-B = 3, then the value of the algebraic formula 8-2a + 2b is
Such as the title

8-2a+2b
=8-2(a-b)
=8-2(3)
=8-6
=2

A school held a spring sports meeting, class A and class B students went to the supermarket to buy a certain brand of beverage, the supermarket sales method is as follows: buy no more than 30 bottles, press zero
If you buy more than 30 bottles but not more than 50 bottles, you will get 20% off the retail price; if you buy more than 50 bottles, you will get 60% off the retail price. Class a will buy 70 bottles of drinks twice in two days (more than the first day in the second day), and pay 183 yuan in total, while class B will buy 70 bottles at a time?

First judge 182 / (3 * 70) > 0.8, so enjoy a 20% discount
x*3+(70-x)*3*0.8=182
x=25
70-25=45

2x-y = 0 3x-4y = 2

2x-y = 0
3x-4y=2②
From 1
y=2x/3
Substituting in (2)
3x-8x/3=2
x/3=2
x=6
thus
y=4
Namely
x=6
y=4

There are 11 students borrowing books from the book corner. To ensure that at least one student can borrow three books, how many books should there be at least in this book corner?