In the school library, science and technology books account for 1 / 3 of the total number, comic books account for 2 / 5 of the total number, and what percentage of the total number are science and technology books and comic books?

1/3+2/5=11/15
A: Science and technology books and comic books account for 11 / 15 of the total

Extend the Ba side of ABC to D point, CB side to e point, AC side to f point, and get the result of triangle def

The area of ACD should be twice that of ABC
The area of the triangle ade is three times that of the triangle ADC. Similarly, the area of the triangle DEF is four times that of the triangle ade
The area of triangle DEF is 2 × 3 × 4 = 24 times that of triangle ABC, that is 240 square centimeter

(x-1) 100 * 90% = 100 * 80% to solve the equation

(X-1)100*90%=100*80%
9（x-1)=8
9x-9=8
9x=17
x=17/9

A triangular piece of glass, measured its bottom is 14.8 decimeters, the height is 8. According to 0.5 yuan per square decimeter, how much does it cost to buy this piece of glass?

14.8 * 8.5 * 1 / 2 = 62.9 (square decimeter) the measure of area
62.9 * 0.5 = 31.45 yuan

Add + - * / () to 10 eights to make the number equal to 2001

[(8+8)*(8+8)-8]*8+8/8+8+8=2001

In the triangle ABC, ab = AC, BD is the center line on the side of AC. BD divides the circumference of ABC into 36 and 63 parts, and calculates the length of BC

BD divides the perimeter of ABC into two parts: ab + ad, AB + ad = AB + 1 / 2Ac = 3 / 2Ab, CD + BC = CD + 1 / 2Ac = CD + 1 / 2Ab. There are two cases: when AB + ad is 36, CD + BC is 63, 3 / 2Ab = 36, ab = 24, BC = 63-1 / 2Ab = 63-1 / 2 * 24 = 51

Given a (1,2), B (2,3), C (- 2,5), we prove that △ ABC is a right triangle

It is proved that: ∵ AB = (2-1, 3-2) = (1, 1), AC = (- 2-1, 5-2) = (- 3, 3), ∵ ab · AC = 1 × (- 3) + 1 × 3 = 0, ∵ ab ⊥ AC. ∵ ABC is a right triangle

Trapezoid ABCD, AD / / BC, diagonals intersect o, triangle AOD area is 20, triangle ABO area is 30. Calculate triangle BCD area. The figure is an isosceles triangle connected by diagonals
It's an isosceles trapezoid, not an isosceles triangle

If the area is 75 and the ad side length is 10, the area ratio of AOD and ACD is 2:5, so the side length ratio of AOD and BOC is 2:3, the area ratio is 4:9, and the area ratio of BOC is 45. The result is 75

. lgx-1 / x = 0, we obtain the domain a (0,1] B (1,10] C (10100] d (100, + ∞)

According to the dichotomy, Let f (x) = lgx-1 / X
F(1)=0-1=-10
F(1)F(10)

There is a rope and a bamboo pole. After folding the rope four times, it is 2 meters shorter than the bamboo pole. How long is the bamboo pole? How long is the rope?

You have come up with a condition
There is a rope and a bamboo pole. When the rope is folded in half, it is 2 meters longer than the bamboo pole. When the rope is folded in four, it is 2 meters shorter than the bamboo pole. How long is the bamboo pole
How long is it?
Let the rope be x meters, and the length of the bamboo pole be equal
There is an equation
(x/2)-2 = (x/4)+2
De denominator
2x-8=x+8
x=16
Then the length of bamboo pole (x / 2) - 2 = (16 / 2) - 2 = 6m
The rope is 16 meters long

In the school library, science and technology books account for 1 / 3 of the total number, comic books account for 2 / 5 of the total number, and what percentage of the total number are science and technology books and comic books?