Questions about math in the first grade of junior high school, math problems in the first grade of j

1, loss 2, loss loss3 Second, the distance between A and B is 9 kilometers.

Analysis: 1. Profit = 60-60 (1 + loss = 60 (2. Profit = a-a (1+ loss = a ( Because a is a positive number, the loss is greater than the profit; Profit = 60-60 (1+m%) = 60m 1+m% Loss = 60 (1-m%) - 60 = 60m 1-m% Because 1-m% < 1+m%, the loss is still greater than the profit.

3. Loss = a ( , so make a profit.

2. First turn the hours into minutes, that is, the speed of descent is 1 5 kilometers per hour, the speed of the flat road is 3 20 kilometers per hour, the speed of the flat road is 2 15 kilometers per hour, the speed of the uphill is 1 15 kilometers per hour, and the return time is 90 minutes.

Let the mountain road be x kilometers and the flat road be y kilometers, then the equation can be obtained: 5x+20 3*y=55,15 2*y+15x=90 solve the equation system to get x=3, y=6. The distance between A and B is x+y=9

1.Lost. 2.Loss.

2. 9 km.

Set the mountain road for x kilometers and the flat road for y kilometers.

x/12+y/9=55/60

x/4+y/8=

Solve the equation. x=3 y=6 So the distance between the two places is 9 km.

If the yield of the first field stove mold is x kilograms, and the yield of the second field is y kilograms, then x+y=470,, and the elimination yuan is x=250, y=220, so the yield of the first field increases by 40 kilograms, and the yield of the first two experimental fields increases by 22 kilograms.

You set the yield of the first field to x, and the yield of the second field is (62-x), divide them by their growth rate, and add them to 470 to calculate x.

The yield of the first field before the improvement was a

Then the second block yielded 470-a

1+16%)a+(1+10%)(470-a)=532a=250, so the first piece of the shed before the improvement of Lianxiao was 250 kg.

The second return block yields 532-290 = 242 kg.

Mathematical method: analysis: each pigeon cage originally lived six pigeons, now each pigeon cage exactly eight, indicating that the original remaining 3 plus the flying 5 as long as assigned to the original pigeon cage, each pigeon cage to add 2, 8 2 = 4, means that there are 4 pigeon cages.

3+5) (8-2) = 4 (cages.

4 * 6 + 3 = 27 (pigeons.

Calculation: 27 + 5 = 32, 32 8 = 4 cages.

Equation method: with x pigeon cages, the equation is: 6x+3=8x-58x-6x=3+5

2x=8x=44*6+3=27

If the original x pigeon cage is 6x+3+5=8x, then x=4

There were 24 + 3 = 27 pigeons and 4 pigeon cages.

Solution: There are x pigeon cages.

6x+3=8x-5

6x-8x=-5-3

2x=-8x=44 6+3=27 (only).

A: There were 27 pigeons and 4 baskets.

It's a matter of harmony.

Cage: (3+5) (8-6)=4

Pigeons: 6*4+3=27

Solution: Set up the original x pigeon cages. Equation: 6x+3+5=8x, solved x=4. 4 6 + 3 = 27 (only) A: There are 27 pigeons, 4 pigeon cages.

There were 27 pigeons and 4 cages.

If there are x pigeon cages, we can calculate that there are 4 pigeon cages, and 4 times 6 plus 3 equals 27 is the number of pigeons.

The original 27 pigeons and 4 pigeon cages, with x pigeon cages, then there is the equation 6x+3+5=8x, and the solution is x=4, then there are 4*6+3=27 pigeons!

1. When x 20: A shop: 120x; Shop B: 100x.

When x 20: A shop: 120 20+120; Shop B: 100 20+100.

2. If you need to buy Y pair, then 120 20 + 120, calculate y=70

3. Buy in store A: 120 20 + 120 for rackets plus 100 balls, and 1000 yuan for another 200 balls, a total of 9160 yuan.

Buy at store B: 100 20 + 100 for rackets plus 200 balls, and 500 yuan for another 100 balls, for a total of 8900 yuan.

So you should buy it at store B.

1, when 02).120*20+120*(x-20)*Solution x=3)A: 120*20+120*(300-20)*B: 100*20+100*

So A is a good deal.

If you are speechless, you can discuss the first question by category.

The second question is very simple based on the first question.

The third question is based on the discussion of the first question.

It's very simple.

1.A(x-120*20)*60%+120*20 B: (x-120*20)*80%+120*20

2.Solution: Suppose that when buying x rackets, the two stores will cost the same amount.

From the meaning of the question: x-120*20)*60%+120*20=(x-120*20)*80%+120*20

Solution: x=2400

3.A: 120*20 + [(120*80)*60%]+300-100)*5=9400 yuan.

B: 120*20+[(120*80)*80%]+300-100*2)*5=8580 yuan.

Because 9400 is greater than 8500 yuan.

Therefore, you should choose B store to save money.

1) Discussion of the situation:

1. When x"=20: A: 120x B: 100x2, when x"20, A: 120*20+120*(x-20)*B: 100*20+100*

2).120*20+120*(x-20)*Solution x=3)A: 120*20+120*(300-20)*B: 100*20+100*

So A is a good deal.

1) A: 20 120 + (x-20) 120 B: 20 100 + (x-20) 100

2) When W A = W B, then: 960 + 72x = 400 + 80x x = 70 When X = 70 W A = W B.

3) W A: 20 120 + (100-20) 120 yuan), from the title, there are 100 tennis balls, then you also need to buy W tennis = 200 5 = 1000 W A total = 8160 + 1000 = 9160 (yuan).

W B: 20 100 (100-20) 100 yuan), from the title, there are now 200 tennis balls, then you also need to buy w tennis = 100 5 = 500 w B total = 8400 + 500 = 8900 (yuan).

w A w B choose B.

1) b 2) 10 9 * 10 3 = 10 (9 + 3) = 10 12 , multiply with the power of the base, add the invariant index of the base, so choose c

1. b simplification (x 2 + 3 x + 2) (x + a) = x 3 + (3 + a) x 2 + (3a + 2) x + 2a, there is no constant term there is no 2a, so a = 0

2. C10 9 10 3=10 12 times.

Perfectly squared formula, a 2 + 2 ab + b 2 = (a + b) 22k-3 = 16, k = 19 2

The black sail is half the length of the side of the big square.

Why can't you see the picture?

Such questions are generally about finding a bottom edge.

It is enough to make them equal to the bottom and the same height (that is, to divide an edge into 4 equal parts, and then the height corresponding to them is the same height and absolute thickness.

Sorry you can't upload **.

Divide the square into four squares.

Father one. The two sons A and B occupy three-quarters of the square adjacent to their father, and the other two sons, C and D, occupy half of the square opposite to their father, plus A and B occupy the remaining four circles of the square as one-part.