There is no one in the classroom, only Li Yan is doing her homework seriously

There is no one in the classroom, only Li Yan is doing her homework seriously

There is no one in the classroom
Only Li Yan is doing her homework seriously in the classroom

There was no one in the classroom, only Wang Jun was still doing his homework

Correction: the classroom is quiet, only Wang Jun is still doing his homework there
Cause: contradiction

A and B vehicles are running from AB to ab at the same time. They meet in 4 hours. This is the midpoint of the distance of 10km. It is known that the speed of a and B vehicles is 7:8. Find the distance between a and B
My answer is 300km. What about you?

Let V A = 7K, v b = 8K
The equation is: 4 × 7K + 10 = 4 × (7K + 8K) △ 2
The solution is k = 5,
∴s=4×（7×5+8×5）=300km

The circumference of an isosceles triangle is 16cm, one of which is 5cm long, 4cm high and () cm2 in area
The perimeter of an isosceles triangle is 16cm, one of which is 5cm in length, 4cm in height and () cm2 in area
Please help me

Given that ABC is an integer a + B = 65, C-B = 49, a-c = 94, what is the square of the sum of ABC?

Add a + B = 65 and C-B = 49 to get a + C = 114, then add a-c = 94 to get a = 104, and then replace it with B = - 39 and C = 10, so the square of the sum of ABC is 5625

How to solve the problem of tree planting?

To solve the problem of tree planting, we only need to master certain rules, mainly including the following formula
Unilateral linear tree planting: tree = total length / interval + 1 total length = (tree-1) * interval
Unilateral circular tree planting: tree = total length / interval total length = tree * interval
Bilateral tree planting: just put the number of trees planted on one side * 2

Cut the largest circle on a piece of square paper with a side length of 8 cm. How much less is the area of the circle than that of the square

3.14*4*4=50.24
8*8=64
64-50.24=13.76
13.76/64=0.215=21.5%

Let a ＞ 0, B ＞ 0, n ∈ n * and N ≥ 2, compare the size of n-1 power of B of the nth power of a + n-1 power of a of the nth power of B + n-1 power of a of the nth power of B and 1 of a + 1 of B

b^(n-1)/(a^n)+ a^(n-1)/(b^n)-1/a-1/b
= b^(n-1)/(a^n)+ a^(n-1)/(b^n)-a^(n-1)/(a^n)- b^(n-1)/(b^n)
=[ b^(n-1)- a^(n-1)]/ (a^n)+ [ a^(n-1)- b^(n-1)]/ (b^n)
=[ a^(n-1)- b^(n-1)] [ (a^n)-(b^n)]/(ab)^n
∵a>0,b>0,
A-B has the same sign as a ^ (n-1) - B ^ (n-1), (a ^ n) - (b ^ n),
[ a^(n-1)- b^(n-1)] [ (a^n)-(b^n)]>0,(ab)^n>0,
∴[ a^(n-1)- b^(n-1)] [ (a^n)-(b^n)]/(ab)^n
b^(n-1)/(a^n)+ a^(n-1)/(b^n)>1/a1/b

In a shopping mall, there is a discount of 50% for clothing and 80% for stationery. Xiaoming has to pay ()
A. 184 yuan B. 256 yuan C. 316 yuan D. 440 yuan

320 × 50% + 120 × 80% = 160 + 96 = 256 (yuan) a: the actual cost is 256 yuan

The cylinder is a 15.7-decimeter-long square. The surface area of the cylinder is______ ．

5 (decimeter) 3.14 × 2.52 × 2 + 15.7 × 15.7 = 39.25 + 246.49 = 285.74 (square decimeter) answer: the surface area of the cylinder is 285.74 square decimeter. So the answer is 285.74 square decimeter