How do you do these math problems? It s better to have ideas!! Simple solution!

7770 Multiples of 3 and multiples of 5, multiples of 3 all numbers add up to multiples of 3 (simple algorithm, such as 12 1+2 3=1), so there are at least 3 7s, which are multiples of 5, and the end must be 0, so it is 7770

As above, the combined numbers are 0 3 2 7 and 2 3 7 9 and 2 7 0 9, 2037 2073 2079 2097 2307 and so on, and the fourth is 2097

99, I don't know how the big brother above got it, ask him, I copied it in this little copy, for the sake of beauty.

2008-10 = 1998 1998 2 3 3 3 37 = 1, the common divisor of 1998 is 32, m = 32

Even number, the number of times to cross the river back and forth to the north bank is a multiple of 2, and the number of times to cross the river back and forth is 2 times. The odd number definitely stopped on the South Bank, and in 2003 it was the odd number, and it stopped at the South.

The difference between these 5 odd numbers is 2, the minimum difference is the largest number of 4 2s, and the last few are 3 2 1 2, (85 + 2 * (4 + 3 + 2 + 1)) 5 = 21, which is the largest odd number, (85-2 * (4 + 3 + 2 + 1)) 5 = 13 is the smallest.

A, should be B 3 guns are 9 rings can achieve 27 rings, for the truth, there is only one true, then the fake is A.

The odd number is at least 2 more than the even number, and when the odd number is only 2 more than the even number, the even number is the maximum, (200-2) 2=99 The even number is at most 99.

Even number, let represent m people, to shake hands m-1 times, all handshakes = (m-1) * m, one is an odd number, one is an even number, and the odd number and even number are multiplied to be an even number.

The last one is an odd number. It should be n*(n-1) 2, permutations and combinations.

1. A positive integer is composed of 0 or 7, and it is divisible by 15, then the minimum number of such a number is (7770) (process: divisible by 15, then divisible by 3 and 5 at the same time, the sum of the digits must be a multiple of 3, and the end is 5 or 0).

2. There are five numbers, from which four different numbers are selected to form different four-digit numbers that are divisible by 3, these four-digit numbers are from small to large, and the fourth number is (2097) (process: from small to large in order of 、...

3. Divide 2003 by a positive two-digit number, and the maximum remainder that can be obtained is (96) (process: "99" is definitely not right!) The remainder should be less than the divisor, which is what I learned in elementary school!! ）

4. In order to celebrate the success of Beijing's bid for the 2008 Olympic Games, the teacher asked a question; 2008 is removed by m natural numbers, and the remainder obtained is 10. The maximum value of m (1998) is calculated (process: the remainder is 10, i.e. 1998 is divisible by these numbers, and there are 11 divisors greater than 10 in the divisor of 1998).

5. The ferry boat goes back and forth to and from both sides of the river, if it initially starts from the north bank and returns to the north bank several times, then the number of times the boat crosses the river is (even number) (odd or even), if it starts from the north bank and crosses the river 2003 times and then stops at the (south or south) bank. (Process: Isn't the sum of n times that go once and again?).

6. The sum of five consecutive odd numbers is 85, of which the largest number is (21) and the smallest number is (13) (process: the number in the middle is 85 5 17, note that there are 5 consecutive odd numbers here, so it should be ).

7. As shown in the figure is a target paper, the score on the target paper indicates the score of the target area. A said; I took 6 shots, scored on each shot, and scored a total of 27 points. B said; I took 3 shots, scored on each shot, and scored a total of 27 points.

Only one of them is telling the truth, and it is (A) who is telling the lie (process: A shoots 6 shots, since the score of each shot is an odd number, then A's score should be the sum of 6 odd numbers, which must be an even number).

positive integers, their sum is 5000, in these numbers, odd numbers are more than even numbers, so how many even numbers are there at most? (95) (process: a total of 200, odd numbers are more than even numbers, then even numbers are less than 100, and because sum is 5000 is an even number, so the number of odd numbers is even, at least 102, even numbers are up to 98).

9. At a conference, the delegates greet each other Wu Shou, then the sum of all the delegates shaking hands with others is odd or even. (even number) (process: simply double the number of the representative door is an even number).

divisible by 15, then divisible by both 3 and 5, the sum of the digits must be a multiple of 3, ending with 5 or 0).

、... from smallest to largest

3. When the divisor is 96, there is a maximum remainder of 83

99" is definitely not true! The remainder should be less than the divisor, which is what I learned in elementary school!! ）

The remainder is 10, which means that 1998 is divisible by these numbers, and there are 11 divisors greater than 10 in the divisor of 1998).

5. Even numbers, South Bank (simple, not explained).

The number in the middle is 85 5 17, note that there are 5 odd numbers in a row, so it should be ).

7. A A fired 6 shots, and since the score of each shot is an odd number, then A's score should be the sum of 6 odd numbers, which must be an even number).

There are 200 in total, and there are more odd numbers than even numbers, so there are less than 100 even numbers, and because the sum is 5000 is an even number, the number of odd numbers is an even number, at least 102, and the maximum number of even numbers is 98).

9. Even numbers (simple, not explained).

1 Round bar volume = volume of the rising part of the water surface.

Find l is the length of the round bar. l=18

2 cone volume v=sh3, s bottom diameter, h height (the length of the jujube here is beaten).

v=Hohu 2*40 3

Weight stool no = volume * density = result.

Because horn 1 = angle 2, so angle oed = angle ofb, because the trillion group is high for angle a = angle c, angle aod = angle cob, so angle d = angle b

Therefore, the triangle OED is equal to the triangle family ruler ofb

So bo=do

Let the side length of the second square be x

Then the side length of the square is x+24

x+24)^2-x^2=960

x=8, the side lengths of Gao Meng are 8 cm and 32 cm, respectively.

Base area =

Side area = bottom circumference * height.

1884cm^2

To make such an insulated bag, at least how many red 1884 square centimeters and black cloth 314 square centimeters should be used.

Base area =

Side area = bottom circumference * height.

1884cm^2

At least how much red 1884 square centimeters to use, black cloth 314 square centimeters.

Red should be: square centimeters.

Black required: (20 2) square centimeters.

(1) Start 5 minutes early, you can do:

70 5 = 350 meters.

1) (2) The distance traveled together is:

1550-350 = 1200 meters.

The time taken is:

1200 (70+80) = 8 minutes.

1) Done again:

8 70 = 560 meters.

1) Home away from school:

350 + 560 = 910 meters.

Let 1's home be x meters away from school, then 2's home will be (1550-x) meters away from school x 7-5 = (1550-x) 80

8x-2800=7（1550-x）

8x-2800=10850-7x

15x=13650

x=910

The home of Set 1 is x meters away from the school.

x/70=(x+1550)/80+5

8x=7x+10850+2800

x=13650

The school is 13650 meters away from the school.

It can be seen as a disguised pursuit problem:

Regardless of the front: the two are 1500 meters apart.

1 is 5 minutes ahead of the other, that is, 1 goes first: 70 * 5 = 350 meters left: 1200 meters.

Then 1 and 2 walk together, walking 150 meters per minute.

Also need 1200 150 = 8

1 walked for 13 minutes, 1 left school: 70*13=910

Set 2 x meters from the school.

x/80+5=x/70

Solve x1's home away from school is x+1550

If 1 and 2 schools are in the same straight line, then 70*(1550+50*7) (80-70)+350=13650

5 * 70 = 350 (m) 1550-350 = 1200 (m) solution: set a total of x minutes.

70x+80x=1200

150x=1200

x=1200/150

x=8(8+5)*70=910(m).

A: 1's home is 910 meters away from the school.

Does the distance to the school have anything to do with the distance between the two of them?

The first 6 rows have a total number:

1 2 3 4 5 6 (hail 1 6) 6 2 21 (pieces) So the first number in row 7 is: 22, and the second number is 23.

7, 2) The real number represented by the source finger is 23.

Solution: according to: 1, 3; 3,5 ;5(a), it can be deduced: a=7 according to: the diagonal of the second and fourth of Xiaoshen: 3,5;5，7；7, (b), it can be deduced: b=9

Root Command: 5 4 = 20;7 8 = 56, it can be deduced: c = 9 12 = 108 so: Heng Sheng laughs c = 108

Solution: Since an operation is specified: a*b=(a+b)-(a-b), then (b-a) in (b-a)*(a+b) is equivalent to a, and (a+b) is equivalent to b, so (b-a)*(a+b)=(b-a+a+b)-(b-a-a-b)=2b-(-2a)=2b+2a, then a*b+(b-a)*(a+b)=2b+2b+2a=4b+2a.

According to its definition, * is an operation that is different from multiplication, and other operations are unchanged a*b=(a+b)-(a-b)=2b

b-a)*(a+b)=（b-a+a+b)-(b-a-a-b)=2b-(-2a)=2b+2a

then a*b+(b-a)*(a+b)=2b+2b+2a=4b+2a

a*b=(a+b)-(a+b), that is, it defines the multiplication of two numbers, which is equal to the sum of the two numbers minus the difference between the two numbers.

Then (b-a)*(a+b)=[(b-a)+(a+b)]-b-a)-(a+b)]].

2b-(-2a)

2b+2a is substituted into the original formula: the original formula = (a+b)-(a-b)+2b+2a=2a+4b