The last question on page 47 of supplementary exercises of mathematics in Volume 1 of sixth grade of Jiangsu Education Press There is a two digit number. The number on the one digit is 2 / 3 of the number on the ten digit. If the number on the ten digit minus 3, it will be equal to the number on the one digit. What's the two digit number? Tonight's homework is urgent! Give us a helping hand! Please be serious, OK?

Let the number on a digit be 2x / 3
2X of x-3 = 3
1 / 3 x = 3
X = 3 divided by 1 / 3
X = 3 times 3
x=9
2X of 3 = 2 of 3 times 9 = 6
A: the double digit is 96

1. A reservoir is 10 meters long, 8 meters wide and 2.3 meters deep. Cement is applied around and at the bottom. What is the area of the cement part?
2. If the length, width and height of a rectangular iron block with a surface area of 94 square decimeters are doubled, what is the surface area of the rectangular iron block now?
Can answer as far as possible to answer only one will write the serial number and then write the answer

1) 10×8+10×2.3×2+8×2.3×2
=80+46+36.8
=162.8 square meters
2) 94 × 2 × 2 = 376 square decimeters

The quotient of number a divided by number B is 0.4, and the simplest integer ratio of number a to number B is______ ．

Number a △ number b = number A: number B, = 0.4, = 25, = 2:5; so the answer is: 2:5

The area of a triangle is 150 square decimeters, the bottom is 15 decimeters, how many decimeters is the height? Use the equation to solve

15X÷2=150

How to solve the equation of 1.2 divided by 4 plus 2x = 5?

1.2÷4+2X=5
0.3+2X=5
2X=4.7
X=2.35
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The circumference of a semicircular sheet of iron is 20.56 decimeters. How many square decimeters is the area of this sheet of iron?

How to simplify 5 out of 10 math problems in Grade 5 of primary school

5 out of 10 numerator and denominator divided by 5
=1 / 2

As shown in the figure, in RT △ ABO, Ao = 30, Bo = 40, ∠ AOB = 90 °. Find the sum of perimeter of five small right triangle

First of all, there is a problem in finding the sum of the circumference of five small right triangles. Where are the five small right triangles? Only RT △ ABO can be found, and only the circumference of △ ABO can be found
Find the length of AB first: according to Pythagorean theorem
The square of AB = the square of Ao + the square of Bo
=900+1600
=2500
Then we open the arithmetic square root of AB, and we get
AB=50
Perimeter: 30 + 40 + 50 = 120

The reasoning process of proving inequality by analytic method is to seek the reason that makes inequality hold
A. Necessary condition B. sufficient condition C. sufficient and necessary condition D. necessary or sufficient condition

The basic steps are: to prove All you need is a certificate Only need to prove The analytical method is to find the sufficient conditions for the existence of the inequality from the inequality, and transform the problem of proving the inequality into the problem of judging whether these sufficient conditions exist or not. Therefore, the theoretical basis of the "analytical method" is to find the sufficient conditions or necessary and sufficient conditions for the conclusion

It is known that s △ doc = 15 square centimeter, Bo = 23bd

Let H be the height of the trapezoid, which is also the height of △ DBC, because ob = 23bd, BD = Bo + OD, so Bo = 2od, and because in △ AOD and △ DBC, ad ‖ BC, Bo = 2od, so ad = 12bc, because △ doc is equal to △ BOC, Bo = 2od, s △ doc = 15 square centimeter, so s △ BOC = 2 △ doc = 2 × 15 = 30 (square centimeter), because s △ DBC = s △ doc + s △ BOC, so s △ DBC = 15 + 30 = 45 (square centimeter), and Because s △ DBC = 12 × BC × h, so 12bch = 45, because the area of trapezoid ABCD = 12 (AD + BC) h, so the area of trapezoid ABCD = 12 (12bc + BC) h, = 32 × 12bch, = 32 × 45, = 67.5 (square centimeter), a: the area of trapezoid is 67.5 square centimeter