There are 800 story books in the library. The number of science and technology books is 58 of story books and 25 of comic books. How many comic books are there?

There are 800 story books in the library. The number of science and technology books is 58 of story books and 25 of comic books. How many comic books are there?

A: there are 1250 comic books

（m-2n）（m+n）=?

The original formula = M & # 178; + mn-2mn-2n & # 178; = M & # 178; - mn-2n & # 178;

(1994 + 1 / 1992) * 1992 / 1993 simple method

(1994+1/1992)*1992/1993
=(1993+1993/1992)*1992/1993
=1993*1992/1993+1993/1992*1992/1993
=1992+1
=1993

157×23156．

157 × 23156 = (156 + 1) × 23156 = 156 × 23156 + 23156 = 23 + 23156 = 2323156, so the answer is: 2323156

2003×20042004-2004×20032003．

2003×20042004-2004×20032003=2003×2004×10001-2004×2003×10001=0．

Given that real numbers a and B satisfy 0 < a < B + 1, try to judge the size of a & # 178; - 1 and B & # 178; + 2B

b²＋2b－﹙a²-1﹚=﹙b＋1﹚²-a²＞0∴a²-1＜b²＋2b

The sum of 7.2 plus 8.1 divided by 9 is calculated by a simple method

（7.2+8.1）÷9
=7.2÷9+8.1÷9
=0.8+0.9
=1.7

Given that the quadratic function y = (m-2) x & # 178; + 5x + 3 has two intersections with the X axis, then the value range of M is

∵ quadratic function y = (m-2) x & # 178; + 5x + 3 has two intersections with X axis
∴△＞0
∴△=5²-4×3（m-2）＞0
That is, m < 49 / 12
∵m-2≠0
х m ＜ 49 / 12 and m ≠ 2

(1) 3 / 8 of a number is 45. What is 1 / 5 of the number? (2) 1 / 4 of 26 minus 2 / 3 divided by 1.5,
What's the difference?
(1) A car from a to B, in the morning of the whole line of 1 / 2, in the afternoon of the whole line of 1 / 3, at this time from B there are 200 kilometers. A, B road length of how many kilometers?
(2) The supermarket brought in 750 kg of apples and pears. After selling one fifth of them, the ratio of the remaining apples and pears was 5:7. How many kg of the remaining apples and pears?

1. 3 / 8 of a number is 45. What's 1 / 5 of this number?
45 △ 3 / 8 × 1 / 5
=24
2. What's the difference between 1 / 4 of 26 minus 2 / 3 divided by 1.5?
26 × 1 / 4-2 / 3 △ 1.5
=6.5-4 / 9
=6 and 1 / 18
solve the problem
(1) A car from a to B, in the morning of the whole line of 1 / 2, in the afternoon of the whole line of 1 / 3, at this time from B there are 200 kilometers. A, B road length of how many kilometers?
200 ÷ (1-2 / 1-3 / 1)
=200 △ 1 / 6
=1200 (km)
(2) The supermarket brought in 750 kg of apples and pears. After selling one fifth of them, the ratio of the remaining apples and pears was 5:7. How many kg of the remaining apples and pears?
750 × (1-1 / 5) = 600 (kg)
Remaining apples: 600 ÷ (5 + 7) × 5 = 250 (kg)
Remaining pears: 600-250 = 350 (kg)

A cuboid, 4m in length and 3M in width. What is the largest and smallest floor area?

The solution cuboid is 4m in length, 3m in width and 2m in height. Its largest floor area is 4m in length × 3m in width = 12m;
The minimum area is 3M wide × 2m high = 6m & # 178;