Changchun Publishing House English 2009 Primary School Graduation and Further Education Necessary Reference Answers

1, the sum of a and b is 389.4. If the decimal point of A is shifted one place to the right, it is equal to B, and A is (35.4).

Analysis:

If the decimal point of a number is shifted to the right by one place, it will be enlarged by 10 times. If it is equal to B number, B number is 10 times of A number, and 389.4 corresponds to the sum of multiples of A and B. Therefore, a number: 389.4 ÷ (10+1) = 35.4.

2. It took the car five hours to go from A to B and four hours to return from B to A, and the speed when returning was (25)% faster than when driving.

Analysis:

The speed is 1/5 when going, and 1/4 when returning.

( 1/4- 1/5)÷ 1/5=25%

3. Two cars, A and B, leave from A and B relatively at the same time. After an eight-hour meeting, the two cars moved on. It will take another 6 hours for the A train to arrive at B, and it will take (18 and 2/3) hours for the B train to arrive at A. ..

Analysis:

When two cars meet within 8 hours, it is known that the sum of the speeds of the two cars is 1/8, and it will take another 6 hours for a car to arrive at B. It is known that it takes (8+6)= 14 hours for a car to get from A to B. It is also known that the speed of a car is114.

1÷( 1/8- 1/8+6)=56/3

Namely: eighteen and two thirds.

4. There are two thirds of books in Zhang Li, four fifths in Li Qiang and many books (in Zhang Li).

Analysis:

Use ratio and proportional knowledge to compare.

Letter from Zhang Li ×2/3= Letter from Li Qiang ×4/5.

Letter from Zhang Li: Letter from Li Qiang =4/5:2/3=6:5.

The number of letters from Zhang Li is 6, and that from Li Qiang is 5, which means there are many letters from Zhang Li.

5. There are 27 people who have an outing by car for one day. There are two kinds of vehicles for rent. Each van can take 8 people, and the daily rent is 80 yuan. Each car can take four people, and the daily rent is 50 yuan. Renting (3) vans, (1) cars is the most economical, and it should cost (290) yuan.

Analysis:

Divide 27 people into 8 people, with 3 groups and more than 3 people.

That is 27=8×3+3.

Divided into four groups, there are five groups with more than seven people.

That is 27=4×5+7.

How much should it cost to compare several ways of renting a house?

One: 3 vans+1 car * * * 290 yuan.

Two: 5 cars+1 van takes 330 yuan.

Three: Rent four vans for 320 yuan.

Four: Rent seven cars for 350 yuan.

Compare the first one to save money.

6. There are two shopping malls selling goods. The first mall has bought enough goods from 50 yuan to return 10 yuan; The second shopping center offers a 10% discount on all goods. There is also the same suit, which is sold in both shopping malls 120 yuan. According to the preferential terms, it is cheaper to buy this suit from the (first) shopping mall.

Analysis:

The first mall will return to 10 yuan after buying enough 50 yuan, that is, return to 20 yuan at 100 yuan, so it should cost 120-20 = 100 yuan to buy this suit.

The second shopping mall will give a 10% discount, which is 10% of the price of cheap goods, so we use 120×90%= 108 (yuan).

It is cheaper than the first one.

7. 15 consecutive natural numbers, the largest number is three times the smallest number, and the sum of these 15 natural numbers is (2 10).

Analysis:

First find the minimum number 14÷(3- 1)=7.

7+8+9+……+2 1=2 10

Namely: 2 10

8. If two natural numbers are divided, the quotient is 4 and the remainder is 3, and the sum of the dividend, divisor, quotient and remainder is 100, then the dividend is (75).

Analysis:

Because dividend = quotient ... remainder.

Dividend = Divider× Quotient+Remainder

According to the meaning of the question

(divisor × quotient+remainder)+divisor+quotient+remainder = 100

Solution: let the divisor be X.

X×4+3+X+4+3= 100

5X+ 10= 100

X= 18

Bonus: 18×4+3=75.

9. There are three boxes of fruit, A, B and C. The ratio of box A to the sum of boxes B and C is 1:5, box B to the sum of boxes A and C is 1:2, and box A to box B is (1:2).

Analysis:

According to the first condition, A+B+C =6 copies.

According to the second condition, A+B+C =3 copies.

Then A accounts for 1/6 of the total, and B accounts for 1/3 of the total.

a:B = 1/6: 1/3 = 1:2。

10. In the subtraction formula, the sum of the minuend, subtraction and difference is 144, the ratio of difference to minuend is 5:9, and the product of subtraction and difference is (1280).

Analysis:

According to the ratio of difference to minuend, it is 5:9.

It can be inferred that the subtraction is 9-5=4.

Proportional distribution method

5+9+(9-5)= 18

( 144×4/ 18)×( 144×5/ 18)= 1280

1 1. Two piles of coal * * * have 1300kg. When the first pile burned two thirds and the second pile burned five sevenths, the remaining coal was the same. How many kilograms are there in the two piles of coal?

Solution: Let the first pile and the second pile have X and Y kilograms respectively.

① 1/3x=2/7y

②x+y= 1300

It is obtained from equation 2: x =1300-y.

1/3×( 1300-y)-2/7y = 0

y=700

x: 1300-700=600

A: The first pile is 600 kilograms, and the second pile is 700 kilograms.