A batch of story books and science and technology books have been delivered to the bookstore, of which 60% are story books. Science and technology books are 85 less than story books. How many books are there in this batch?

85 divided by (60% - 40%) = 85 * 5 = 425 copies

Xiao Ming bought some story books and interesting mathematics for 50 yuan. The salesman found 8 yuan. Please help Xiao Ming judge how to find it. My original title is incomplete

Is the money recovered right? If not, how much should be recovered?
or
Get the money back, right? Then find out the price of all kinds of books

The Three Gorges of the Yangtze River is located in
A. Between Yibin and Chongqing B. between Yichang and Wuhan C. between Yichang and Chongqing D. between Nanjing and Wuhan

The Three Gorges of the Yangtze River is 204 kilometers long, starting from Fengjie County in Chongqing City in the West and ending in Yichang City in Hubei Province in the East. From west to East, there are three major Gorges: Qutang gorge, Wuxia gorge and Xiling Gorge. The Three Gorges are named after this. The two sides of the Three Gorges are facing each other with steep cliffs. The peak is 500-1000 kilometers above the river. The narrowest part is less than 100 meters, The upper reaches of the Yangtze River in China are called Qutang gorge, Wuxia gorge and Xiling Gorge for short. It starts from Baidi Town, Fengjie County, Chongqing City in the West and ends at nanjinguan, Yichang County, Hubei Province in the East, with a length of 204 km. Qutang gorge is called from Baidi town to Daixi, Wuxia is called from Wushan mountain to Badong Guandu estuary, Xiling Gorge is called from Xiangxi to nanjinguan in Zigui. The elevation of peaks on both sides is 1000-1, It is 500 meters long, with steep cliffs and tight river surface. The narrowest part is only about 100 meters. There are many winding channels and dangerous beaches. In the boat gorge, there is a realm of "no way out of stone, no sky in clouds"

How to prove that the equivalent infinitesimal of 1-cosx is 0.5x

When x → 0 (1-cosx) / (x ^ 2 / 2)
=2[sin(x/2)]^2/(x^2/2)
→1,
1-cosx and x ^ 2 / 2 are equivalent infinitesimals

One ninth of one third is (), one ninth is one third (several parts), and one ninth of () is one third
Five eighths of a number is forty-five, and three fourths of the number is ()
One fifth of the number a is equal to one sixth of the number B. the number a is 90 and the number B is ()
Brothers and sisters, help our motherland~

One ninth of one third is (1 / 27), one ninth is one third (1 / 3), and one ninth of (3) is one third
Five eighths of a number is forty-five, and three fourths of the number is (54)
One fifth of the number a is equal to one sixth of the number B. the number a is 90 and the number B is (108)

11\13-31 11\12+(-30 10\11)-(-29 11\13)-(-28 11\12)-27 1\11
0-32 11\13-31 11\12+(-30 10\11)-(-29 11\13)-(-28 11\12)-27 1\11

3 black iron above 6 and below 10, 4 corals, 4 death gloves, Youming Necklace 1 weapon special repair this is 31 32 is 2 memory necklaces, 4 death gloves, 4 corals, 4 Black minerals above 10 and below 15. 33 is 4 memory necklaces, 5 corals, 5 death, 4 mines around 18! 34 is a pair of 7 death gloves, 5 memory items of dragon ring finger

If there are 2n + 1 items in the arithmetic sequence, the sum of all odd items is 132, and the sum of all even items is 120, then n = ()
A. 9b. 10C. 11d. Uncertainty

Suppose the sequence tolerance is D, the first term is A1, the ∵ arithmetic sequence has 2n + 1 terms, the odd terms have n + 1 terms, the sum of which is s odd = (n + 1) (a1 + A2N + 1) 2 = (n + 1) an + 1 = 132, the even terms have n terms, the sum of which is s even = n (A2 + A2N) 2 ∵ Nan + 1 = 120, the sum of which is s odd s even = n + 1n, that is s odd s even = n + 1n = 132120, the solution is n = 10, so choose B

There are 50 pieces of RMB 2 yuan and 5 yuan in Xiaoming's piggy bank. The total amount is 160 yuan. How many pieces of RMB 2 yuan and 5 yuan each?

Set 2 yuan x sheets, 5 yuan 50-x sheets
2X+5(50-X)=160
2X+250-5X=160
3X=90
X=30
30 sheets for 2 yuan, 20 sheets for 5 yuan

Fill in the regular numbers: 1 / 2, 0.4, 37.5%, 4 / 11, 5 / 14 (), ()

Fill in the regular numbers: 1 / 2, 0.4, 37.5%, 4 / 11, 5 / 14 (), ()
Regular filling: 1 / 2, 2 / 5, 3 / 8, 4 / 11, 5 / 14 (6 / 17), (7 / 20)

Given that the function f (x) x ∈ r satisfies f (x) = 2bx / AX-1, a ≠ 0, f (1) = 1, and that f (x) = 2x holds only one real number, if the sequence {an} satisfies A1 = 2 / 3,
A (n + 1) = f (an), BN = 1 / an-1, NX belongs to n *, it is proved that A1B1 + a2b2 + +anbn

1 = f (1) = 2B / (A-1), a = 2B + 1.2x = f (x) = 2bx / (AX-1), X is not equal to 1 / a.2ax ^ 2 - 2x = 2bx, 0 = ax ^ 2 - (1 + b) x = ax [x - (1 + b) / a], (1 + b) / a = 0, B = - 1, a = 2B + 1 = - 1. F (x) = - 2x / (- x-1) = 2x / (x + 1). A (n + 1) = f [a (n)] = 2A (n) / [a (n) + 1]. If a (n + 1) = 0, then a (n) = 0

A batch of story books and science and technology books have been delivered to the bookstore, of which 60% are story books. Science and technology books are 85 less than story books. How many books are there in this batch?