A primary school math application problem. Ask

The volume of the cuboid length, width, and height, after analyzing the meaning of the question, we will find that the length, width, and height of the cuboid cannot be directly calculated from the known conditions in the question. At this time, we might as well start from the known conditions and find another shortcut to solve the problem. Now let's analyze it together:

If the length increases by 2 cm, the volume increases by 40 cubic centimeters, and the width and height are 40 2 20 (square centimeters); If the width increases by 3 cm, the volume increases by 96 cubic centimeters, and the length and height are 96 3 32 (square centimeters); If the height increases by 4 cm, the volume increases by 96 cubic centimeters, and the length and width are 96 4 24 (square centimeters). From this, according to the surface area of the cuboid (length, width, height, width, height) 2, the surface area of the cuboid can be found to be (24 32 20) 2 152 (square centimeters).

Solution: The length, width and height can be set to l, d, and h. respectivelyThe original volume was v

According to the topic, the volume volume increases by 2 when the length increases by 2 * width * height, and the volume increases when the width increases by 3.

Length * 3 * height, when the height increases by 4, the volume increases length * width * 4; Therefore.

2*Width*Height = 40(1).

Length * 3 * height = 96 (2).

Length * width * 4 = 96 (3).

The surface area of the cuboid = 2 (length * width + length * height + width * height) = 2 * ((96 4) + (96 3) + (40 2)) = 152 (square centimeters).

40 2 = 20 (square centimeters).

96 3 = 32 (square centimeters).

96 4 = 24 (square centimeters).

20 + 32 + 24) * 2 = 152 (square centimeters).

A and B two barrels of oil totaling 60 kilograms, poured out of barrel A 5 kilograms, barrel B of oil is three times that of barrel A, A and B Yuan Feng's letter has (and kilograms, 5 + (60-5) (3 + 1).

kilogram) kilogram).

A and B are two barrels of oil with a total of 60 kilograms, and 5 kilograms are poured out from barrel A (to B), and the oil in barrel B is three times that of barrel A, and A and B originally had (20 and 40) kilograms respectively, 60 + 5 + 3 * 5) (3 + 1).

20 (kg).

40 (kg).

Analysis: 450 chickens and ducks, if you buy 30 ducks, then there are 450 chickens and ducks + 30 = 480.

The inscription says that if half of the chickens are sold at this time, the chickens are twice as many as the ducks, and in the case of no chickens being sold, it means that the chickens in the 480 chickens are 2*2=4 times that of the ducks. So 480 was divided into five parts, and one was the number of ducks. It is also easy to find the number of chickens.

Solution: (450+30) (2x2+1) = 96 (current number of ducks) Number of chickens: 96 4 = 384.

Number of ducks: 96-30 = 66.

After selling half of the chickens, you buy 30 ducks, and the chickens are twice as many as the ducks, which means that the original chickens are four times that of the current ducks, and if you don't sell half of the chickens, then the chickens account for four-fifths of the total number of chickens and ducks (450 + 30 = 480) (480 5 * 4 = 384), and there are (450-384 = 66) ducks.

450 + 30 = 480 480x2 = 960 960 divided by 384 equals 384 so 384 chickens and ducks 450-384 = 66.

Let the eldest spend $x, the second spend $y, and the third spend $z, with x=(y+z+65) 2, that is, 2x-y-z-65=0 (1)y=(x+z+65) 3 x-3y+z+65=0 (2).

z=(x+y+65) 4 x+y-4z+65=0 (3) The solution of the simultaneous equation yields:

x = 100 yuan, y = 75 yuan, z = 60 yuan, the four brothers spent a total of x+y+z+65=100+75+60+65=300 yuan.

Solution: Set up the boss, the old.

Second, the third child spent x, y, and z yuan respectively, then.

x=1/2(y+z+65)

y=1/3(x+z+65)

z=1/4(x+y+65)

x=100 for solving a system of ternary linear equations

y=75z=60

So the four brothers spent a total of 100 + 75 + 60 + 65 = 300 (yuan).

A mathematician's tombstone is engraved with the following passage: I had a happy childhood in the first seven years of my life, and I spent a quarter of my life studying after my childhood, after that, I got married, and after 5 years of marriage, I had a child, and I felt very happy, but unfortunately my child was only half of my time in the world, and after the child died, I spent 4 years in sorrow, and then ended my life.

Can you calculate the age of the mathematician and his children???

The eldest spent 1 share, the other three spent 2 shares, a total of 3 shares, the eldest accounted for one-third of the total, and so on, I learned: the second spent a quarter of the total, the third spent one-fifth of the total, the three people accounted for a total of 47/60 of the total, the fourth accounted for 13/60, and the total amount of money can be calculated by dividing the money spent by the fourth child by 13/60. 300 yuan.