A few math problems!! 15. A few math problems!!

Eight years ago, eight years later, after a total of 16 years, the son was 16 years older, and if the father was 16 4 64 years older, it would still be 4 times longer, and now it is only 2 times.

Son after 8 years: (64-16) (4 2) 24 years old.

Son this year: 24 8 16 years old.

Father's age: 24 2 8 40 years old.

It's a question of profit and loss: if there are 10 rooms that are not occupied, there are 10 3 30 people less.

40 (3, 1) 20 rooms.

1 Solution: Suppose the son was x years old 8 years ago.

4x+16=(x+16)x2

4x=2x+16

2x=16x=8

8x(6-1)=40 (years).

8+8=16 (years).

A: The father is 40 years old and the son is 16 years old.

2 Solution: There are x dormitories.

x+10=3x-10

x=3x-20

3x-x=20

x=10A: There are 10 dormitories.

1.The father is now x years old and the son is now y years old.

x-8)=4(y-8)

x+8)=2(y+8) x=40 y=16 dormitories.

x+10=3x-10 x=10

3.Why is there only one topic? ~

I really don't know, forget to Ladu, recall the bitter days of the college entrance examination that year, haha.

The father is 40 years old and the son is 16 years old.

There are 20 dormitories with 30 people.

Question 3: I don't understand.

Study hard, how can students always rely on the Internet.

The purchase price is X yuan, and the price is X + 960 yuan.

According to 80%** of the list price, then according to the selling price: 80% * (x+960) yuan** loss: x-80%*(x+960)=832 yuan, x=8000

The purchase price of this product is 8000 yuan.

It means that the 20 percent is 960 + 832, because if you add 832 and add 960, the 20 percent will be made up.

The original number of girls was six-sevenths of the number of boys, seven of the boys, and six of the girls. It turns out that the ratio of girls to boys is 6:7

6:7 of 6 [score] share thought that adding 6 [number] people would become 20:21 [20:41's 41 is the ratio of all grades, and subtracting 20 is the ratio of boys].

Therefore, subtracting the ratio before adding 6 people is equal to the score of 6 people, and the formula is: 20:21-6:7=2:21

According to a sentence: the corresponding number divided by the corresponding score is equal to the unit 1, and now it is found, 6 is the corresponding quantity, and 2:21 is the corresponding score, with 6 2:21 = 63 people. 63 is the number of boys in unit 1.

Since the number of girls is six-sevenths of the number of boys, six-sevenths of the number of boys who know is equal to the number of girls. 63 6 7 = 54 = number of girls.

Now the original girl boy knows. Adding it up is the original total number, 54 + 63 = 117 people.

Let's set the number of girls x and the number of boys y

x/y=6/7

x+6）/ （x+y+6）=20/41

x=6/7y

x+6）/ （x+y+6）=20/41

6/7y+6）/ （6/7y+y+6）=20/416/7y+6=120/287y+20/41y+120/41-14/287y= -126/1

y=63x/y=6/7

x/63=6/7x=54

A: There were 117 students in the sixth grade of Qinghe Primary School.

There were originally 117 people.

Set up the original girl x person, the original boy y person.

x=（6/7）y

x+6)/(x+6+y)=20/41

Solution: x=54, y=63

Then: x+y=117

If there are x number of boys and 6 7x girls.

6/7x+6):(6/7x+6+x)=20:41x=63 6/7x=54

So there were 117 students.

Solution: Set up the original x number of girls.

41－20）（6x＋6）＝20×7/6x21×6×6/7（x＋1）＝20

108x＝88

x＝22/27

Because the number of people is an integer, there is no practical solution to this problem.

Let the original boy x girl 6x 7

Then 6x 7 +6 : x = 20:41 has no positive solution.

It turns out that female: male = 6:7 = 18:21

Now female: male = 20:21

2 more copies are 6 people, the original 39 copies = 39 * 3 = 117 people.

Yuan) - the amount of money payable by Xiaoya.

50-32 = 18 (yuan) - the amount of money that should be recovered.

Your question is missing the thickness of the book, and according to your answer, the thickness of the book is 2cmSolution: the rectangle to be cut.

The width is: (a-6) 2+3 2+2=2a-12+6+2=2a-4 and the length is: (a+10)+3 2=a+16

Area = (a+16) (2a-4) = 2a 2-4a + 32a-64 = 2a 2 + 28a-64

Healthy Healthy

2.Solution: Let the length of the first block after subtracting x meters be 4 times that of the second block.

148—x=4(100—x)

x=84148—84=64 (m) 100—84=16 (m).

1.Originally, the height of the water and the height of the water were 1:1, so the height of the water was 1 2 of the total height and later became 3:2, so the height of the water was 3 5 of the total height (the difference came from **, that is, from pebbles).

The difference is 3 5-1 2 = 1 10

So the volume of a pebble is 1000x1 10 = 100 cubic centimeters.

2.A's efficiency is 1 4, while B's efficiency is 1 5, so (1 5) (1 4) = 4 5

3.b, the concentration is definitely sweeter, and it has nothing to do with the amount of sugar water, because no matter how much, the sugar content in the unit sugar water is still the same, and 15% is definitely sweeter.

1000 3 2 = 1500 cubic centimeters.

3. C may be as sweet as the quantity is not known to be?