Nine and eighteen nineteen times five

Nine and eighteen nineteen times five

=(1 / 10-19) × 5
=10 × 5-1 / 19 × 5
=5 / 50-19
=49 and 14 / 19

How to calculate (7 / 13 + 9 / 19) * 13 * 19 easily?

Distribution law by multiplication
7/13 *13*19+9/19 *13*19=7*19+9*13=133+117=250

19.45-7.5-9.45-2.5 =? Simple calculation

19.45-7.5-9.45-2.5
=（19.45-9.45）-（7.5+2.5）
=10-10
=0

Simple calculation of 9.9 × 9.9 + 19.9

9.9×9.9+19.9
=9.9×（10-0.1）+19.9
=9.9×10-9.9×0.1+19.9
=99-0.99+19.9
=99+18.91
=117.91

Solution equation: (78 + 90 + 82 + 80 + x) / 5 = x + 6
Be specific

(78+90+82+80+X)/5=X+6
330+x=5x+30
5x-x=330-30
4x=300
x=75

The area of a triangle vegetable field is 540 square meters. The height of the bottom edge is 30 meters, and the length of the bottom edge is 40 meters______ ．

540 × 2 / 30, = 1080 / 30, = 36 (m), a: the bottom edge of this vegetable field is 36 m long, so the answer is: 36 M

How to calculate 25 * 125 simply

25*（100+25）=2500+625=3125

As shown in figure (1) ⊿ ABC, ∠ ABC = 45. H is the intersection of high AD and be. (1) please guess the relationship between BH and AC and explain the reason. (2) if the
As shown in figure (1) ⊿ ABC, ∠ ABC = 45. H is the intersection of high AD and be,
(1) Please guess the relationship between BH and AC and explain why
(2) If ∠ a in figure (1) is changed to an obtuse angle, please draw the figure of the problem in figure (2). Is the conclusion in figure (1) still valid? Please explain the reason
Please design a survey plan to find out how the whole school goes to school (walking, cycling or riding). What kind of way are you going to use?
General survey and sampling survey

Equal, prove BDH congruent ADC. (2) also become, and (1) same, prove BDH congruent ADC

Inequality a (5x2 + Y2)

a(5x^2+y^2)≤x^2+4xy
That is, ay ^ 2-4xy + (5a-1) x ^ 2 ≤ 0
∵x≠0 ,y≠0
Divide both sides of the original formula by x ^ 2 at the same time
It is tenable that a (Y / x) ^ 2-4 (Y / x) + 5a-1 ≤ 0
Let t = Y / X ∈ (- ∞, 0) U (0, + ∞)
The original inequality is
at^2-4t+5a-1≤0
When a = 0, that is - 4t-1 ≤ 0, it is not tenable
When a > 0,
F (T) = at ^ 2-4t + 5a-1 is a parabola with the opening upward,
It is impossible for f (T) ≤ 0 to be constant
When a

A trapezoid, after its bottom is shortened by 5 cm, becomes a square, and the area is reduced by 20 square cm. What is the area of the original trapezoid?

20 × 2 / 5 = 8 (CM), (8 + 5 + 8) × 8 / 2, = 21 × 8 / 2, = 84 (square cm); answer: the original trapezoid area is 84 square cm