Super easy 5th grade math problems

First of all, B played for 5 hours.

That's left. 2 3 is made of A.

2 3 1 12 = 8 (hours).

A will have to fight for 8 hours.

4 hours, B alone for 5 hours to indicate that the task has been completed 1 3 (5*1 15), and then divide by A's work efficiency 1 12

1-5 15) (1 12) = 8 hours.

B played for 5 hours, that is, he played all 5 15, so A only needs to do the rest by himself.

It takes 8 hours.

B played for 5 hours, that is, he played all 5 15 = 1 3, and there was 2 3 left, so A only needs to complete 2 3 of the time by himself, that is, 12 * (2 3) = 8 hours.

Equation: It takes x hours to complete the armor.

1-5/15=x*1/12

Gives x=8

A's efficiency is: 1 divided by 12

B's efficiency is: 1 divided by 15

Set the armor to hit x hours.

1/15）*5+（1/12）*x=1x=8

Solution: The effect of one hour is 1/15, so 5 hours is 2/3 of the work left.

Let the workload be 1 minus 1/3 = 2/3

Multiplying 12 times 2/3 equals 8 hours.

B takes 15 hours to complete alone. B played for 5 hours first and completed 1 15*5 1 3

2 312 * 2 3 8 hours remaining.

Question 1:

Solution: 2r + solution r = 10cm

Note: Don't forget that the circumference of the semicircle is the diameter of the circle + the arc length of the semicircle Question 2: The first rope is left 9 and 3 4 meters.

Third question: 9 4=

So x=the first question I've made clear.

The circumference of the semicircle is the diameter of the circle (that is, twice the radius of the circle) + the arc length of the semicircle (I don't need to say this, right?). )

Let the radius of the semicircle be r (that is, the x in the equation, the fifth-grade equation has been learned, right?) Then 2r+ is 2x+pi)*x=

Solution r=10

x=10) semicircle circumference formula c=2r + pi) r

Area formula. s = squared) 2

Solution: Because, the first one decreases by 4, and the second one increases by 3.

Therefore, after the first one is reduced to the second one, there will be one more (4 3 1) and because the third one is reduced by half, then the number of these three pencils is equal, which is equivalent to dividing it into 4 equal parts, and each part is 12 pieces.

i.e., (49 1) 4 12

Then, the first pencil is: 12 + 4 16 (pieces).

The pencils in the second hand are: 12 3 9 (pieces).

The third pencil is: 12*2 24 (pieces).

In fact, this question is the assessment of the "number of copies", don't be paralyzed because the question is given 3 copies, you can actually split it into 4 copies. Hope it helps!

49-4+3=48 (the total minus 4 plus 3 is the corresponding to the remaining number of bundles.) 48 4 = 12 (Originally, there were three bundles of pencils, but the last third bundle was as many as the two bundles of any other, which is actually equivalent to having the same number of bundles, so divide by 4 and it is the current number of threads in each bundle.) ）

Therefore, the original first bundle had 12 + 4 = 16

Second bundle 12-3 = 9

The third bundle is 12 + 12 = 24

Without equations, I won't

You can make do with it and see that when the number is equal, the three pencils are all x, and then the number is restored to the original state, the first one: x+4

Second: X-3

The third hand: x*2

These three add up to 49: (x+4)+(x-3)+(x*2)=49 This equation should be solved, x=12

Then let's substitute the above three formulas: the three pencils are 16, 9, and 24 (I hope it helps you

All light flares.

My answer should be correct.

The key to this question is that the total length of the cube and the cuboid frame is the same as the edge length of 6cm, the cube frame is 12 edges, it can be seen that the total length of the wire is 6 * 12 = 72cm The cuboid is also 12 edges, of which 4 are long and 4 are wide, and the remaining 4 are now known to be 5cm long and 3cm wide, so (5 + 3) * 4 = 32cm and 72-32 = 40cm are left, and the 40cm is the 4 heights that make it high, each of which is 40 4 = 10cm

The total length of the steel wire is 6 times 12 (4 each for length, width and height), and the total length of the steel wire remains unchanged after becoming a cuboid, and the total length = (length + width + height) multiplied by 4 to find the height.

6 * 12 = （5 + 3 + x ) 4x = 10

The length of the original iron wire is 72cm

If the height is n, then x4+4n=72 gives that n is equal to 10cm

Solution: Because the length of the wire is the same, the circumference of the cube is equal to the circumference of the cuboid, i.e.

4 3 (12 edges) 6 = 4 (5 (length) + 3 (width) + x (height)).

x=10cm

The volume of the original water + the volume of the cube of iron - the total capacity of the water tank.

l) A: total overflow l.

The volume of water is 8*6*

The volume of the cube iron block is 4*4*4

The volume of the glass cylinder is 8*6*4

8*6*liters.

Nani: It's such a simple question, and I don't even have a 4th grade number.

Calculate the remaining volume first: 8*6*(

Subtract the remaining volume from the volume of the iron block to get the volume of water flowing out: 4*4*

A matchbox, length, width, height, if the length, width, height of the inner box is regarded as the length, width and height of the coat, calculate the area of the cardboard used in the inner box and the outer box how many square meters. [Paste is not counted].

Answer: Inner box area s inner box = 2 * (

Cm. Square metre. Outer box area s Outer box = 2 * (square centimeters, square meters.)

2.Use 4 2 cm cubes to form a cuboid, there are several spellings, and the surface area of the cuboid is what is each

Answer: There are 5 ways to spell it.

Length 4 width 4 height 2, S table 1 = 2 * (4 * 4 + 4 * 2 + 4 * 2) = 64 square centimeters.

Length 4 width 2 height 4, S table 2 = 2 * (4 * 2 + 4 * 4 + 2 * 4) = 64 square centimeters.

Length 2 width 2 height 8, S table 3 = 2 * (2 * 2 + 2 * 8 + 2 * 8) = 72 square centimeters.

Length 2 width 8 height 2, S table 4 = 2 * (2 * 8 + 2 * 2 + 8 * 2) = 72 square centimeters.

Length 8 width 2 height 2, S table 5 = 2 * (8 * 2 + 8 * 2 + 2 * 2) = 72 square centimeters.

3.A cuboid wooden block, respectively, along with the up and down, left and right, front and back parallel directions each cut a knife, the surface area increased by 240 square centimeters, the original cuboid meter fast surface area is how many square centimeters

Answer: A rectangular wooden block, cut one knife along the direction parallel to the top and bottom, left and right, front and back, respectively, the increased surface area is 4 side areas and 2 bottom areas, therefore, the increased surface area is equal to the original surface area, so the original surface area of the rectangular block is 240 square centimeters.

1. Inner box area = bottom area) + (side area) = square centimeter coat area = square centimeter.

2. Two methods:

The first type: arrange 4 cubes in a row to form a cuboid with a length of 8 heights and 2 widths of 2, with a surface area of 2 * 2 * 2 + (2 + 2) * 2 * 8 = 72 square centimeters.

The second type: 4 cubes are arranged together to form a rectangle in the shape of a field from above, with a surface area of 4*2*4+4*4*2=64 square centimeters.

3. According to the upper and lower parallel cutting a knife, 2 surface areas equal to the upper and lower areas are added, and in the same way, the left and right, front and back are cut with a knife, and each adds a surface area equal to the left and right, front and back areas, so it can be known that the total increased surface area of this cuboid is the original surface area, then, the original surface area is 240 square centimeters.

1. The inner box has five sides, and the outer box has four sides, and the area of the inner box is s=2*(

Cm. Square metre. Outer box area s Outer box = 2 * (square centimeters, square meters.)

2.Answer: There are 5 ways to spell it.

Length 4 width 4 height 2, S table 1 = 2 * (4 * 4 + 4 * 2 + 4 * 2) = 64 square centimeters: length 4 width 2 height 4, s table 2 = 2 * (4 * 2 + 4 * 4 + 2 * 4) = 64 square centimeters:

Length 2 width 2 height 8, S table 3 = 2 * (2 * 2 + 2 * 8 + 2 * 8) = 72 square centimeters: length 2 width 8 height 2, s table 4 = 2 * (2 * 8 + 2 * 2 + 8 * 2) = 72 square centimeters: length 8 width 2 height 2, s table 5 = 2 * (8 * 2 + 8 * 2 + 2 * 2) = 72 square centimeters 3

A cuboid wooden block, respectively, along with the up and down, left and right, front and back parallel directions each cut a knife, the surface area increased by 240 square centimeters, the original cuboid meter fast surface area is how many square centimeters

Answer: The increased surface area is 4 side areas and 2 base areas, so the increased surface area is equal to the original surface area, so the original surface area of the box block is 240 square centimeters.

1.Draw the image yourself, look at the length of each part, it is very simple to calculate the area of the rectangle, the area of the coat is square centimeters, and the area of the inner box is square centimeters.

2.Two types of 2x2x8: the surface area is 72 square centimeters, 4x4x4: 96 square centimeters.

3 This topic requires a little imagination, and for each cut, there are two more parallel areas of 2, and the original surface area is 240 square centimeters.

1. Outer box area: . Inner box area:.

2. A, 80cm

3. The two sides added by each cut are equal to the sum of the front and back of the original cuboid, the sum of the left and right sides, and the sum of the upper and lower sides, so the surface area of the original cuboid is equal to the increase of 240 square centimeters.

1. Imagine the shape of a matchbox first.

Inner box: no top surface (the top side) S inside (the result is calculated by yourself) Outer box: no two sides S outside

2. Two spellings.

The first spelling: four cubes are arranged in a row, and the result is 8 in length, 2 cuboids in height and width, and a surface area of 2*(8*2+2*2*2) 48;

The second spelling: 2 on the bottom and 2 on the top. The surface area is s2*(4*4+4*2*2) 64.

3. The original surface area of the cuboid was 240 square centimeters.

Cut a knife in the parallel direction of the top and bottom, and add 2 upper faces; Similarly, one knife is cut in the direction parallel to the left and right, and the front and back are parallel, adding 2 sides and 2 front sides respectively.

1.(square centimeters A: The area of the cardboard used in the outer box is square centimeters.

Square centimeters A: The area of cardboard used in the inner box is square centimeters.

1. The inner box is (square centimeters.

The outer box is (square centimeters, converted to square meters.

1.Inner box:

Cm. Outer box: = square centimeters.

The unit is self-contained.

1.This should be considered according to the old-fashioned matchbox, the inner box is less than the outer box, the lid is less than a length by width, and after I have calculated it, I will pay attention to the transformation into m good egg pain.

The area is 72 square centimeters and the volume is 32 cubic centimeters.

3.No change 240

1. an outer box.

Inner box species 72 and 64

Cm.

1, self-calculation 2, two, the area is 64 and 72 3,240*2=480 respectively

The last one, which is easiest not to count, is 240, because the added surface area is exactly the area of the faces of the original box.

Why do you ask this kind of question

2.There are two kinds. 8*4=Same as the same

3.== It's hard.