Math problems, try to solve them in elementary school methods

1. (a - 3 5) m a (1-3 5) = 2 5a (m) The first 3 5 meters represent the specific number, and the total is a, and how much is left with 3 5 meters is subtracted.

The second 3 5 means that the total length of 3 5 is used, and there is 2 5 left, that is, what is the 2 5 of a.

2. If there is a total of x kg of rice, think like this: the first time you take out 40% x, 30 bags are not finished, the remaining 15 kg, the weight of 30 bags is (40% x-15), and each bag is loaded: (40% x-15) 30

The total is 50 + 30 = 80 bags Average bag: x 80 Establish the equation: (40% x-15) 30 = x (50 + 30) 40% x-15) 80 = 30x

32x-1200 =30x

2x =1200

x=600

1.If a rope is a meter long, if 3 5 meters are used, there is still ((2a) 5 meters left; If you use its 3 5, there are still (((4a) 25)) meters left.

a*(1-3 5)=(2a) 5m.

2a) 5)*(1-3 5)=((2a) 5)*(2 5)=((4a) 25) meters.

2.Dafeng supermarket wants to bag a batch of bulk rice, and the quality of each bag of rice is required to be the same. For the first time, 40 of the total amount of rice was taken out, and 30 bags were filled with 15 kilograms; The second time all the remaining bulk rice was filled with exactly 50 more bags (each bag of rice was of the same mass as the first one).

How many kilograms of rice are in this batch?

This batch of rice has a total of x kilograms.

Then: (x*40%-15) 30)*50=x*(1-40%)+15(

20*x-750=18*x+450

2*x=750+450=1200

x = 600 kg.

This batch of rice totals 600 kilograms.

1、a-3/5，2a/5

A meter long rope, 3 5 meters were used, and the rest was (A-3 5) meters; If his 3 5 is used, that is, 3a 5 meters are used, it means that there are (a-3a 5) meters left, which is reduced to (2a 5) meters.

Kilogram. Suppose there is a total of x kg of rice, and the weight of each bag of rice for the first time is: (40% ·x-15) 30

The weight of each bag of rice for the second time is: (60% ·x+15) 50 The quality of the rice is the same twice, so: (40% ·x-15) 30=(60% ·x+15) 50

Solution x=600 (kg).

1.If a rope is a meter long, if 3 5 meters are used, there are (2 5) meters left; If you use 3 5 of it, there is still (3 5a) meters left.

This is the correct way to solve the problem; To use the method of elementary school you said: Sun Ku.

The side length of the square is a

The diameter of the circle is d, and the radius is r, then.

r=d 2 requires the largest circle, then there is d=a

d 2=a 2=12, understand?

Area of the circle = r 2= (d 2) 2= d 2 4 = 12 4=3 (square meters).

I've said it in detail, so if you support me, give me satisfaction. Xie Xiaokai file Xie.

The speed ratio of A and B is.

B to A completed the journey, A traveled the whole journey 2 3

When they meet, the time taken by A and B is the same, because the speed of the two is different, so the distance traveled is not the same, that is, the speed ratio of A and B is 4:6=2:3.

And when a has been reached, B has traveled the distance of ab, that is, the required amount s, so according to the same time, the ratio of distance is equal to the ratio of velocity, which can be columned: 2:3=390:

s, i.e., s=390*(3 2).

A and B are 435 km apart.

Analyze: When A and B meet, A travels 40 percent, then B should be 60 percent, and the speed ratio of A and B is 2:3

When B reaches place A, A has traveled a total of 390 kilometers, and the speed ratio in the same time is equal to the distance ratio, then B has traveled 435 kilometers, which is the distance of AB.

When A and B meet, A travels 2 5 and B travels 3 5, that is, the ratio of A and B trips in the same time is 2:3. When B arrives at place A, A has traveled the whole journey (1x2) 3, and the question tells you that A has traveled a total of 390 km, then the whole distance is 390 (2 3) = (390x3) 2 = 585km.

This is the distance between abs.

The ratio of the speed of A to B is 4:6 (because A has traveled 40 percent and B has traveled 60 percent).

The ratio of distance between A and B is also 4:6 (the same time).

So s = 390 * (4 6) = 390 * (3 2) = 585 km.

1. The area of each face of the cube is 24 6 = 4 (square centimeters), 4 = 2x2, the edge length of the cube is 2 cm, if it is cut into 4 cubes of the same size, then the length, width and height of the original cuboid may be 8 cm, 2 cm, 2 cm, or 4 cm, 4 cm, 2 cm, so the surface area of the promised may be [banquet with surplus (

square meters, or possibly [(square meters.

2. Length: 24 4 (5 + 4 + 3) x 5 = cm), width: 24 4 (5 + 4 + 3) x 4 = 2

cm), height: 24 4 (5+4+3)x3=cm), paper (surface area) :(cm²) =, volume: cubic centimeters) =

2 = 3, 3x3x3 = 27 (pcs), the surface area is increased: 2x2x6x27-6x6x6 = 432 (square centimeters).