The school bought three kinds of books, one fourth of which is literature and art books, one fourth of which is science and technology books, and three fourth of which is story books. Literature and art books are 40 less than science and technology books. How many books are there in total?

Story books = (1 / 4) / (3 / 4) = 1 / 3;
A total of = 40 (1 / 3-1 / 4) = 40 × 12 = 480 copies;
Hello, I'm glad to answer for you. Skyhunter 002 will answer your questions
If you don't understand this question, you can ask. If you are satisfied, remember to adopt it
If you have any other questions, please take this question and send it to me. Please understand
I wish you progress in your study

There are three kinds of books in the library of the school, 15% of which are literature books, 45% are science books, and the rest are story books. There are 480 story books

15 plus 45 = 60 480 divided by 60 = 8 literature and art books: 8 * 15 = 120 science and technology books: 45 * 8 = 360 books, please adopt! Please find a satisfactory answer!

There are 200 story books in the fifth grade Library of experimental primary school. The number of science and technology books is 3 / 5 of story books, and the number of literature and art books is 3 / 5 of science and technology books
How many books

200 times 3 / 5 = 120 [Ben] 120 times 3 / 5 = 72 [Ben]

The fourth power of (- 1) - 1 / 6 × [the second power of 2 - (- 3)]
[Online answer] second back!

The fourth power of (- 1) - 1 / 6 × [the second power of 2 - (- 3)]
=1-1/6×(2-9)
=1-1/6×(-7)
=1+7/6
=13/6

It took 23 seconds for a train to pass through a 342 meter tunnel, and then 17 seconds for it to pass through a 234 meter tunnel. The train missed another 88 meter long train with a speed of 22 meters per second, and asked if it was necessary______ Seconds

The speed of the train is: (342-234) / (23-17) = 108 △ 6, = 18 (M / s); the length of the train is: 23 × 18-342 = 414-342, = 72 (m); the passing time of the two trains is: (72 + 88) / (18 + 22) = 160 △ 40, = 4 (s), a: it takes 4 seconds; so the answer is: 4

If e is a point on BC, de = 2, CE = 1, then the area of square ABCD is ()
A. 3B. 3C. 4D. 5

As shown in the figure, ∵ in the right angle △ DCE, de = 2, CE = 1, ∠ C = 90 °, according to the Pythagorean theorem, CD = de2-ce2 = 22-12 = 3, ∵ the area of square ABCD is: CD · CD = 3

The speed of light propagation in vacuum is 3.0 X10 ^ 8m / S (1). How many meters is a light year equivalent to?
(2) Apart from the sun, the nearest star to the earth is the nearest star in the constellation Centaurus, which is 4.0x10 ^ 13km away from us. How long does it take for its light to reach the earth?

（1）x=ct=9.46x10^15m
One light year is equivalent to 9.46x10 ^ 15m
(2) T = x / v = 4.23 years
It takes 4.23 years for the light to reach the earth

A mobile communication company has set up two kinds of communication services, "global link": the user pays 50 yuan monthly rent first, and then pays 0.4 yuan for each minute of the call; "Fastlink": no monthly rent is paid. It costs 0.6 yuan for each minute of the call. If the call takes X minutes in a month, the call fees of the two methods are expressed by Y1 yuan and Y2 yuan respectively
(1) Write the functional relations of Y1 and Y2
(2) How many minutes to talk in a month? The two mobile communication costs are equal
(3) It is estimated that the call time is 300 minutes in a month. Which kind of mobile communication is more cost-effective?
If it is less than one minute, it will be counted as one minute
I see other answers are not right, not so simple
How to express it?

1)
y1=50+0.4x,y2=0.6x
2)
Y 1 = y 2, Y 1 = 50 + 0.4x, y 2 = 0.6x, solve the equation, x = 250 minutes
3）
When x = 300, substitute it into the equation:
Y 1 = 50 + 0.4 * 300 = 170, y 2 = 0.6 * 300 = 180, Y 1 is less than y 2, so the first one is more cost-effective
This is really the tariff when the mobile company was founded,

In diamond ABCD, the length of side is 5, the diagonal AC is 5, and the area of diamond is calculated

The area sum of two equilateral triangles
S = radical 3 / 4 × 5 × 5 × 2 = 75 / 2 radical 3

Solve equation 6x square-x-2 = 0

(3x-2)(2x+1)=0
x=2/3 x=-1/2

The school bought three kinds of books, one fourth of which is literature and art books, one fourth of which is science and technology books, and three fourth of which is story books. Literature and art books are 40 less than science and technology books. How many books are there in total?