Prawns, let s help me with a few math problems!

1. b ， a

4.2800 yuan.

Solution: Let the salary be x, 60% x + 720 = 6 x 7, > x = 2800 yuan.

My mother's salary this month is 2,800 yuan.

5.Take 200 kg of 75% alcohol and 100 dry grams of 45% alcohol.

Solution: Take 75% alcohol x kilograms, 45% alcohol y dry grams, then 75%x+45%y=65%(x+y), x+y=300

x = 200, y = 100, > take 200 kg of 75% alcohol and 100 dry grams of 45% alcohol.

1) The greatest common factor is b, and the least common multiple is a;

2) The number A is 15. The number of A can be set to 3x, and the number of rigid B is 8x, which can be solved by 8x-3x=25;

3）256。If the length and width are a and b respectively, then there is 2(a+b)=48, s=(a+8)(b+8)=ab+8(a+b)+64=ab+256;

4）2800。If the salary is a, then there is 720 + 60% a = 6a 7, and a = 2800 can be obtained

5) 75% and 45% each have grams. Let 75% have x, and 45% have 300-x, and x=200 can be obtained from 75%x+45%(300-x)=65%*300.

Solution: 1, b, a

4. Set the salary to be x yuan, get (1-40%) x + 720 = 6 7x, and solve x = 1680, so the salary is 1680 yuan.

5. Let the two concentrations be x and y grams respectively, then there are 75%x+45%y=65%*300, x+y=300, and the simultaneous solution is x=200, y=300, so 75% is 200 grams, and 45% is 100 grams.

1: a, b are different non-0 natural numbers, if a is a multiple of b, then the greatest common factor of a and b is (a), and the least common multiple is (a).

2: The number A is divided by the number B, the quotient is 3 8, the number B is 25 more than the number A, and the number A is (40).

3: The circumference of a rectangle is 48 cm, if the length and width are increased by 8 cm each, its area increases by (256) square centimeters?

4: My mother took 40% of this month's salary as a family and deposited the other 720 yuan bonus and the rest of her salary into the bank. The money deposited in the bank is exactly 6 7 of my mother's salary, how much is my mother's salary this month?

720/[6/7-(1-40%)]=720/(9/35)=2800(yuan)

5: There are several grams of alcohol with a concentration of 75% and 45%, and if you want to make 300 grams of alcohol with a concentration of 65%, how many grams should be taken from each of these two alcohols? (The first question is a fill-in-the-blank question).

Solution: Let the concentration of 75% and hen 45% alcohol be x grams and y grams respectively.

According to the title.

1： x+y=300

2: 75%x+45%y=65%x300

Solve xy yourself

1.The greatest common factor is b, and the least common multiple is a

720 divided by 16 35 = 1575 (yuan).

5.Solution: Set 75% alcohol x grams, according to the question.

75%x+45%(300-x)=300x65% solution, x=200300-200=100 (g).

A: Take 200 grams of 75% alcohol and 100 grams of 45% alcohol.

b, a256 (reason: let the length be a, the width is b, the circumference is 48=2 (a + b), after drawing, it can be seen that the increased area is 8a + 8 b + 8 * 8 = 8 (a + b) + 68 = 48 4 + 64 = 256

Let this month's salary be x yuan 6 7x = (1-40%) x + 720 x = 2800300 65% = 195g, and set 75% alcohol xg then 45% alcohol (300-x) g

75%x+45%(300-x)=195 solution, x=200300-x=100g

The 4 balls are arbitrarily numbered, A, B, C, D

Called a, b: the first case: if a = b, then a and b are equally heavy;

2 is called c and d, c cannot be equal to d; If C > D, then C is heavier, D is lighter, if CC, 3 is called A and C, if A=C, then B is heavier, A, C is the same, D is lighter, if AC, then B is heavier, C is lighter, A, D is the same heavy;

The third case: if a>b, that is, b can see this method, in most cases it can be judged by weighing twice, and in a few cases, weighing three times;

Hello big brother. The question can be written like this: Let the weight of the four apples be a, b, c, d, 1, put a, b on the left side of the balance and put it on the right side Because there are 2 apples of equal mass, there are two cases: a+b c+d or a+b c+d remove ac, if the balance is balanced, then put ac into the left and right ends, if a>c, c is heavy, a is clear, and vice versa, a is heavy, and b is light.

Label the apples with ABCD separately

One on both sides of the scale, until the balance is balanced, then the two are the same weight, and the remaining two are placed on both sides of the scale, and the weight can be seen at a glance, then the four apples are distinguished.

Two in a group, divided into two groups.

If two are the same weight in a group.

The first time the two groups are weighed, the two groups can be identified.

If two are the same weight separate in both groups.

The second time the two heavier of the two groups are weighed, the heavier is the heaviest, the lightest one is the lightest in the same group, and the other two are equally heavy.

1 Take out two arbitrarily, put one on each side of the scale, if it is balanced, it means that it is the two that weigh the same weight, then the remaining two are weighed again, one must be heavy and one light.

2 Take out two at random, and if the balance is uneven, replace the light one with the remaining two, so that you can find the heaviest one, and in the same way, you can find the lightest one.

This is only a text explanation, not a list of formulas.

Suppose the lightest is A, the same weight is B, and the heaviest is C.

Take two apples to weigh.

In the first case, if two apples are the same weight, then they are both b. Then weigh the other two, so heavy is C, and light is A.

The second case: two apples, one light and one heavy. Also weigh the other two.

situation, the remaining two apples are the same weight, then they are both B, then the weight of the four apples also comes out, the previous ones were A and C.

case, the remaining apples are one light and one heavy, so use two light ones to weigh. These two are light, and the one that is lighter in it is the lightest A, and the one that is slightly more important in it is the two B that are equally heavy. Then the one who was heavier than B was C, and the one who was heavier than A was B.

1.Mom's second card, Dad's choice of the first card, for the following reasons:

When the mother chooses the first type, the cost is 18 yuan, and the second type is 18 yuan, so it is appropriate to choose the second type.

When Dad chooses the first one, the cost is 40 yuan, and the second one is 60 yuan, so it is appropriate to choose the first one.

2.Greatest common factor: 3 times n squared, which is a 2 least common multiple: b.

1. When the AB card consumption is the same.

16+x=1600/18

Less than 1600 18b card mom.

Greater than the A card daddy.

2 3 times n squared 3 times n to the third power by 5 times 2

3. Set the side length of the cube x

x*2*4=48

x=6, so 216

1.This problem is not brought into the calculation, but in a slightly easier way.

It shows that the cost of the two mobile phone cards is the same when the call minutes are met, and if it does not arrive, the A card is affordable, otherwise the B card is affordable.

So mom uses a card, dad b card.

2.The greatest common factor is 3*(n 2), and the least common multiple is 2*3*5*(n 3)3If the length is a, the width is a, and the height is a+2

2a*a+4a(a+2)-6a*a=48

The solution yields a = 6v = a 3 = 216 cubic centimeters.

The first question is a

The second question has a problem [2n-3 power of A, 8th power of B] This third question is set to deposit x yuan.

72 = x times 20%.

72=x=16000

Question 4: Paragraph 2n+1.

The fifth question is to set A as x to give the answer directly. x=24

1.A's time is set to 1, and B's time is: 1 2 * 1 2 +1 * 1 2 =

2.Screenshot of the question, the meaning of the question is unclear.

5 (x+3)/9=x/8 * 1+1/8)