Seven Answers to Introduction to Mathematics

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The seventh grade mathematics first volume application examination questions

(Score: 100 Time: 90)

Solving application problems with column equations (each problem 10, *** 100)

A store sells two kinds of clothing, A and B, in which the price of A clothing is 120 yuan, with a profit of 20% and the price of B clothing is 120 yuan, with a loss of 20%. How much did the store actually make a profit or lose in this sale?

2. Party A and Party B set out in the same direction with a distance of 50km, with Party B ahead of Party A, Party A left 16km/h and Party B left18 km/h.. If Party B left first 1 hour, how long did Party A leave, and then the distance between them was 70km?

3. A middle school organizes a spring outing for seventh-grade students. If you rent a 45-seat bus, 15 people have no seats. If you rent the same number of 60 buses, except for one bus, the other buses are just full. It is understood that the daily rent for renting 45 buses is 250 yuan, and the daily rent for renting 60 buses is 300 yuan. What kind of bus is more cost-effective? How many cars do you rent?

4. The refrigerator in a certain store first increases the price by 40% on the basis of the original price, and then the advertisement says 20% discount. As a result, each refrigerator earned more 270 yuan. What is the original price of this refrigerator? What's the selling price now?

5. The purchase price of a commodity is 100 yuan. If the profit rate reaches 20%, what should be the selling price of the goods? How much profit can each commodity make at this time?

6. Two-digit numbers. Swap the single digits of a two-digit number with a ten-digit number, and subtract the original number from the obtained number, and the difference is 72, thus finding the two-digit number.

7. There are 60 workers in a workshop, producing a set of supporting products consisting of a bolt and two nuts. Everyone produces 14 bolts or 20 nuts on average every day. How many people should be assigned to produce nuts and how many people should be assigned to produce bolts, so that the bolts and nuts produced every day can just match?

8. The store adjusts the price of goods and sells them at 20% of the original price. At this time, the profit rate of the commodity is 10%, and the purchase price of the commodity is 1600 yuan. What is the original price of this commodity?

9. To process 200 parts, Party A will work alone for 5 hours, and then work with Party B for 4 hours. After completing the task, it is known that Party A will process 2 more parts per hour than Party B. How many parts will Party A and Party B process per hour?

10. It takes 7.5 hours for Party A to complete a job alone, and 5 hours for Party B to complete it alone. First, Party A and Party B work together 1 hour, and then Party B completes the remaining tasks alone. How many hours will it take to finish this task?

Answer prompt

Solution: the cost of a kind of clothing is X yuan, and the cost of B kind of clothing is Y yuan.

x( 1+20%)= 120 x = 100

y( 1-20%)= 120y = 150

∫x+y = 250

The actual selling price is 120×2=240 yuan.

240-250=- 10

∴ Lost 10 yuan in this sale.

Set a walk for x hours, now 70 kilometers apart.

50+ 18× 1+ 18x = 16x+70

x= 1

3. Assume that the X 45-seat bus was originally planned to be rented.

45x+ 15=(x- 1)×60 x=5

(1) (5+1) × 250 =1500 (yuan) (2)4×300= 1200 (yuan)

And 15000 > 1200, therefore, it is more economical to rent a 60-seat bus, and it needs to rent four cars.

If the original price is X yuan, then the current price is (x+270) yuan.

x( 1+40%)×80%-x = 270 x = 2250 x+270 = 2520

Suppose the price of this commodity is X yuan.

X-100 =100× 20% x =120100 = 20 (yuan)

7. Suppose you want to allocate X people to produce nuts.

14×(60-x)×2 = 20x x = 35 60-x = 25

9. Suppose B processes x parts per hour.

4x+9(x+2)= 200 x = 14 x+2 = 16

Answer prompt

Solution: the cost of a kind of clothing is X yuan, and the cost of B kind of clothing is Y yuan.

x( 1+20%)= 120 x = 100

y( 1-20%)= 120y = 150

∫x+y = 250

The actual selling price is 120×2=240 yuan.

240-250=- 10

∴ Lost 10 yuan in this sale.

Set a walk for x hours, now 70 kilometers apart.

50+ 18× 1+ 18x = 16x+70

x= 1

3. Assume that the X 45-seat bus was originally planned to be rented.

45x+ 15=(x- 1)×60 x=5

(1) (5+1) × 250 =1500 (yuan) (2)4×300= 1200 (yuan)

And 15000 > 1200, therefore, it is more economical to rent a 60-seat bus, and it needs to rent four cars.

If the original price is X yuan, then the current price is (x+270) yuan.

x( 1+40%)×80%-x = 270 x = 2250 x+270 = 2520

Suppose the price of this commodity is X yuan.

X-100 =100× 20% x =120100 = 20 (yuan)

7. Suppose you want to allocate X people to produce nuts.

14×(60-x)×2 = 20x x = 35 60-x = 25

9. Suppose B processes x parts per hour.

4x+9(x+2)= 200 x = 14 x+2 = 16

10. Suppose it takes x hours to complete this task.

1+2-3-4+5+6-7-8+......+2005+2006-2007-2

Value 008?

The result of each group is -4, and the total * * * is 2008/4=502 groups.

502*-4+-2008

Oil imports of an oil importing country decreased by 5% this month compared with last month. Due to the rising international oil price, the cost of importing oil this month increased by 14% compared with last month. Find the growth rate of oil price this month relative to last month.

Suppose the oil import volume last month was a and the oil import cost last month was b,

Then the oil import this month is a( 1-5%)=0.95a, and the oil import cost this month is b (1+14%) =1.14b.

Therefore, the oil price growth rate this month =1.14/0.95-1= 0.2 = 20%.

There is a question "When a=2 and b =-2, find the value of polynomial 3A3B3-0.52B+B-(4A3B3-0.25A 2B)+(A3B3+0.25A 2B)-2B2+3". Give reasons

3a^3b^3-0.5a^2b+b-(4a^3b^3-0.25a^2b)+(a^3b^3+0.25a^2b)-2b^2+3

=3a^3b^3-0.5a^2b+b-4a^3b^3+0.25a^2b+a^3b^3+0.25a^2b-2b^2+3

=(3a^3b^3-4a^3b^3+a^3b^3)+(-0.5a^2b+0.25a^2b+0.25a^2b)+b-2b^2+3

=b-2b^2+3，

The value of polynomial has nothing to do with A, so although A is copied wrongly, as long as B is not copied wrongly, there is no calculation.

Wrong, the result is the same as the correct result.

1.BCD are three points on the line AE in turn. Given AE = 8.9 and BD = 3, what is the sum of the lengths of all line segments with ABCDE as the endpoint? (Question 15 on page 62 of Qidong exercise book)

There is an electronic newspaper clock on the bell tower of the railway station. On the boundary of the clock face, a small colored lamp is installed at the scale of every minute. At 9: 35: 20 pm, how many small colored lights were installed in the corner between the hour hand and the minute hand? (Qidong Exercise Book, page 64 16)

1, draw on paper first? ? ? ? ?

A B C D E

Sum of lengths =AB+BC+CD+DE+AC+BD+CE+AD+BE+AE.

=(a b+DE)+(BC+CD)+(AC+CE)+BD+(AD+BE)+AE

=(AE-BD)+BD+AE+BD+(AE+BD)+AE

=8.9-3+3+8.9+3+8.9+3+8.9

=4 1.6

2, 27 or 33

Analysis: According to the title map, according to the scale of every minute, there is a small colored lantern at the hour hand every 12 minutes. Divide by 12 for 35 minutes to get more than two 1, so there are two colored lanterns when the hour hand exceeds 9, and there are five colored lanterns between every two numbers. Work out the answer. Because the angle between the hour hand and the minute hand may be acute or obtuse, there are two answers.

Let rational numbers a, b and c satisfy a+b+c=0, ABC >；; 0, if x = a \iai+b \ibi+c \ici,

Y = a (1/2b+1/3c)+b (1/2c+1/2b), and z is the minimum value of ia- 1i +c(a-3i). Find.

Because A, B and C satisfy a+b+c=0, and abc>0

So at least two of A, B and C are negative numbers.

x = a \u| a |+b \u| b |+c \u| c | =- 1 * 2+ 1 =- 1

y = a( 1/b+ 1/c)+b( 1/c+ 1/a)+c( 1/a+ 1/b)

= a/b+a/c+b/c+b/a+c/a+c/a+c/b

=(b+c)/a+(a+c)/b+(a+b)/c

Because a+b+c=0, b+c=-a, a+c=-b, a+b=-c,

So y=(-a/a)+(-b/b)+(-c/c)=-3.

Z is the minimum value of |a- 1|+|a-3|, so a>0 has a minimum value, |a- 1|+|a-3|=|2a-4|

So when 1