A math problem requires a solution idea, and it doesn t matter if the answer is told or not

Ideas: In this process, the number of girls remains the same, the number of girls is regarded as the unit "1", and then the number of boys is 5 7 of girls, which is less than the original (5 7-60%), it corresponds to the number of 20 people, so use division to find the number of girls, and then find the original number of boys, and then add the number of girls to the number of girls:

175 (person).

Now the number of boys:

125 (person).

Originally, the ratio of male to female students was 6:10, that is, 3:5

Then it can be 3x for boys and 5x for girls

Later, the number of boys was 3x+20, and the number of girls remained unchanged at 5x

You can exemplify proportional formula:

3x+20):5x=5:7

That is, 7 (3x + 20) = 25x

21x+140=25x

The solution is x=35

So 3x=105

5x=175

A: There are now 195 boys.

If there are girls x people, then there are boys, and there are boys (people, according to the question, list the equation:

Cross-multiply, solve, x=175

Now the boys have (people.

A: There are 125 boys now.

Let the boy be a and the girl be b, known: a=

a+20）：b=5:7

Then: (:b=5:7

7 (note here that both sides of the equation are cross-multiplied).

then b = 175a = 105

Then the current boy is 105 + 20 = 125

Use the equation to solve, let the original number of girls be x, and the number of boys is 60%x, and the equation is :

x:60%+20=5:7

What grade are you in? Will it be done??

Removing two zeros from both the divisor and the dividend at the same time means that the divisor and the dividend are reduced by a factor of 100 at the same time.

So the remainder is also reduced by a factor of 100 at the same time.

Therefore, the reduced remainder is 297 (100-1)=3, and the original remainder is 3 100=300

(First of all, know that the absolute values of a and b are non-negative).

When a is greater than 0 and b is less than 0 (b is greater than 0, a is less than 0 and this is the same), the original formula = 1-1 - (-1) = 1

When a and b are both less than 0.

Original formula ==-1-1-1=-3

When a and b are both greater than 0.

Original formula = 1 + 1 - 1 = 1

There is no case of equaling zero, because 0 cannot be the denominator.

Set: There were x people, and the original cost per person was: 6000 x, so:

x-3）（6000/x+100）=60006000-18000/x+100x-300=6000100x²-300x-18000=0

x²-3x-180=0

x-15）（x+12）=0

x1=15x2=-12 is not on topic, discard.

The result was 15 people, and 12 people after 3 people didn't go. Originally 400 per person, later 500.

I'll answer, the following steps:

x is the number of people, after 3 people don't go, the rest of the people need to pay 6000 + 100 yuan.

6000x=(6000+100)*(x-3) after solving x=183

So there were 183 people in total, and after 3 walks, there are 180 people going on a trip.

The sides of the square are equal and are axisymmetric. If the length of an edge changes, its opposite edge changes accordingly. The two adjacent sides have their 1 2 and 1 4 respectively, that is, their opposite sides have increased their 1 2 and 1 4 accordingly.

So, the whole square becomes like this: two of the four sides have the original 1 2 added to each side, and each of the two sides has the original 1 4. Therefore, the circumference has increased by a total of (1 2) * 2 + (1 4) * 2 = 3 2 times.

Assuming that the side length of the original square is 1, the circumference of the new rectangle is 2*(, which is an increase from the original square (

One side increases the length of its original side by half, and the other side increases by half of the original side length, and the new shape is a rectangle. You can set the original side length to 1, then the side length of the increase is 3 2, and the half of the increase is 5 4, so that you can calculate, the original side length is 1, the perimeter is 4, and the length of both sides of the new figure is 3 2 and 5 4, then the perimeter is 3 + 5 2 =. The new perimeter is the original square circumference 4=, increased.

Note: The square in the title is adjacent to both sides, for example, the four sides of a square are in order, then 1 and 2 are adjacent, 2 is adjacent to 3, 3 is adjacent to 4, 4 is adjacent to 1, according to the title, we start from 1, 2 sides, 1 2 side is added to 1 2, 2 sides and 4 sides are adjacent to 1 side, so 1 and 4 sides are 5 4. Then the 3rd side is adjacent to the 2nd and 4th sides, so the 3rd side is 3 2, because the adjacent sides are 1 2 and 1 4 respectively.

All of the above calculations assume that the length of the original square side length is 1 meter.

Let's say the square side length is x (convenient point!) ）

A square is a special shape of a rectangle (i.e., a rectangle), and when one side is grown, the opposite side of the rectangle will grow accordingly!

So when the two sides grow and sum respectively, the corresponding opposite side will also grow and so grow.

It turned out to be a square, with equal adjacent sides. Set to a.

An edge is increased by 1 2 for 3 2a, and an edge is increased by 1 4 for 5 4a.

The circumference of the new rectangle = a * (3 2 + 5 4) * 2 = 22 4a

The original circumference was 4a.

increased by 22 4a-4a=5 4a; (5 4a) 4a = 5 16 increased by 5 16

This is a question of examining the cycle, through these letters, it can be found that the period is 6, i.e., a--b--c--d--c--b, which is a complete cycle. The letter C appears 2 times in each cycle, and the odd number of C is the 3rd letter of each cycle, the even number of C is the 5th letter of each cycle, and when the letter C appears 2010, the cycle goes to the 1005th time, and it is the 5th letter of the 1005th cycle, so the number counted is: 1004*6+5=6029

You'll notice that this string of letters keeps looping in a--b--c--d--c--b--, with a length of 6 and c appearing twice.

At the 2010th occurrence of C, the above letter string is looped to the 1005th time.

Count to 1004 6 +5=6029

One. 200 pcs.

Because: out of these two thousand factors, there are 10, 20, etc

100<10 pcs" 110....200<10" 210....310..

1000 <100" is the same way, to 2000 there are 200 factors with 0).

Two. 366 because: the sum of the front and upper areas is: width multiplied (height + length) = 209, and because the length, width and height are prime numbers, take the width as 3, the length as 61, the height as 2, and the volume as 366).

Three. 20 solution: Let the boy x person, the girl y person, the column equation gets: x + y = 50, 60x + 70y = 63 times 50, solve the system of equations to get, x = 35, y = 15, 20 more people.

Four. 735 because: 2005 divided by 5 = 401; 2005 divided by 6 = 334 to balance 1; 401+334=735)

Five. 2 solution: because: A completes 15/15 in one day, B completes 1/10 in one day, set x days, A completes 15/15 x B completes 10/10 x in one day, and gets x 15 + x 10 = 1 3 solution x = 2

Six. 4 solution: original: up on top up, start: down down down up, down up and down, up and down, up and down, down).

Seven. 3/10

1/2△4+1/3△3=1/2 * 2/3 * 3/4 * 4/5 +1/3 * 2/4 * 3/5=3/10;Regularity, the first number, the denominator plus one, the numerator plus one).

Eight. In 2015, this box sold 104 kg, the remaining 16 sold 103 kg, the remaining 18 sold 101 kg, the remaining 19 sold 100 kg, the remaining 20 sold 99 kg, the remaining 31 boxes sold 88 kg, 104, 103, 101, 100, 99, 88, of which there are only 99 of the three times the number of feet, that is to say, the remaining box is 20 kg).

Nine. Days and years.

Three: Set up male x people and female y people. So x+y=60The boys have a total score of 60x and the girls have a total score of 70ySo the total score of the class is 60x+70yThe second equation is 60x+70y=63 60

Five: Let the total project be 1, so A does 1 15 every day, B does 1 10 every day, and the two work together for x days, so (1 15 + 1 10) x = 1 3

Seven: 1 2 3 = 1 2 2 3 3 4 4 Beishout 5+1 3 2 4 3 5=3 10

VIII: 31 + 19 + 16 = (20 + 18) 2

Nine: C is replaced with a manuscript to roll the key to see the day.

1. Where ten into 0, where 100 into 00, where 100 into 000, where 1000 into 000, so there is a total of 200 at the end

into hundreds, into thousands and into ten repeated).

2. Set the length, width, and height to x, y, and z, and get xz+xy 209 >> x(y+z) 209

It can be seen that the smallest prime number of 209 does not exceed the root number 209, and it is easy to get 209 11*19

So x 11, z=7, y=2

3. Set up x for boys and 50-x for girls

60x+(50-x)*70 50*63 solution x 35, 50-x 15

4. 2005 5 401, 5002 6 332 ......3,401+332＝733

5. Vertical equations x(1 15+1 10) 1 3,x 2

6. Set the first cup as 1, the second as 2, the third as 3, and the fourth as 4, and move the cup in order.

123 for the first time, 234 for the second time, 124 for the third time, 134 for the fourth time, a total of four times.

7. What does it mean? Mausoleum.

8. From the inscription, it can be seen that the first person must have bought 31 kilograms of loans, and the first person bought an even number, so he also bought 19 kilograms of loans, and 32+19+16 (15+18) old heads*2 can be obtained by the elimination method

So in the end, there was 20 kilograms of credit left.

9. 6000 minutes, 50 days, 6000 hours, 500 days, 600 anniversaries.

600 months 50 years.

This is a question with no standard answer

That's it, although it's a little simple, but it took a lot of time, so let's give some points.

Question 3 Equation If there are x boys, then the girl is 50-x Total score: 50*63=3150 60x+(50-x)*70=3150 Solution: x=35 That is, there are 35 boys and 15 girls are prepared to regret Question 4 1 2005 has 2005 numbers: 2005 5=401 2005 6=take 334, that is, to make 401 + 334 = 735 cards.

One. 200 pcs.

Because: among the two thousand Naisha simple factors, the whole ten hundred Youchang pants: 10, 20....

100<10 pcs" 110....200<10" 210....310..

1000 <100" is the same, to 2000 there are 200 factors with 0).

Three. Solution: Set x for boys and 50-x for girls

60x+（50-x）*70=50*63

60x+3500-70x=3150

10x=3150-3500

10x=-350

x=35 50-35=15