Xiaogang and Xiaojun are at the same place. Xiaogang goes south and Xiaojun goes north at the same time. If Xiaogang advances at twice the speed of Xiaojun, it will take three hours The last two are 27 kilometers apart. Find their speed There has to be a process!

If the speed of Xiaojun is x km / h, the speed of Xiaogang is 2x km / h
（x+2X）*3=27
9X=27
X=3
Xiaojun's speed is 3 km / h, Xiaogang's speed is 6 km / h

Xiao Gang read a story book. On the first day, he read 3 / 5 of the whole book. On the second day, he read 1 / 4 of the whole book. There are 39 pages left. How many pages are there in this story book?

The book has 39 / (1-3 / 5-1 / 4) = 39 / (1-12 / 20-5 / 20) = 39 / (3 / 20) = 260 pages

Xiao Gang has a science and technology book with a total of 60 pages. He read 15% of the whole book on the first day and 60% of the whole book on the second day. How many pages did he read in two days?

60 × (15 + 60%), = 60 × 0.8, = 48 pages; a: 48 pages in two days

(5 / 6 + 4 / 5) times 30 = simple calculation

(5 / 6 + 4 / 5) times 30
=5/6×30+4/5×30
=25+24
=49

If a = - 3, B = 3 / 3, find 2005 times of a times 2004 times of B

-Three times of 2004 and one third of 2004 will be multiplied by - 3 and - 3 again and again

Given that a = a + 2, B = - the square of a + A + 1, C = the square of a - 5A + 2, find c-a. when a > 2, compare the size of C and a,
It is known that a = a + 2, B = - A's square + A + 1, C = A's Square - 5A + 2
When a > 2, compare the size of C and a,
Don't you understand?

C-A=a^2-5a+2-a-2
=a^2-6a
=a(a-6)
When a > 2
C-A=a（a-6）
When a is greater than 6. C-A > 0, so c > a
When a is greater than 2 and less than 6, c-a

2.6 plus 1.65 divided by 0.15 is calculated by a simple method

If the equation MX & sup2; + (2m-1) x + M-1 = 0 has only integer roots, then the integer m =?

When m = - 1,0,1, there are only integer roots
Note that when m = 0, the original equation is transformed into:
X + 1 = 0, at this time x = - 1, so also meet the requirements of the topic

Subtract the quotient of a number divided by 2 from 50 to get 13. Find the number! How to make the formula?
3q

（50-x）/2=13 ffffff

A cuboid wooden box without a cover is 0.8 meters long, 5 decimeters wide and 60 cm high. How many square decimeters of wood board does it need to make such a wooden box? How many cubic meters is its volume? (write the formula first and then write the formula)

Hanying warm for you
The formula is the surface formula
0.8 m = 8 decimeters, 60 cm = 6 decimeters
（8×6+5×6）×2+8×5
=（48+30）×2+40
=196 square decimeters
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Xiaogang and Xiaojun are at the same place. Xiaogang goes south and Xiaojun goes north at the same time. If Xiaogang advances at twice the speed of Xiaojun, it will take three hours The last two are 27 kilometers apart. Find their speed There has to be a process!