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<> ABC, AB = 30 cm, BC = 50 cm

ab:bc=3：5

The quadrilateral EBFD is a square.

ed//bc

also ae ab, ad ac

aed∽△abc

ae:ed=3：5

ed=ebae:eb=3：5

eb:ab=5：8

eb=ab5/8

Circumference = 4eb = 4 5 8 30 = 75cm

A class of a mausoleum cave such as a total of 50 people.

There are 11 * 50 10 = 55 people in the second trembling class.

There are a total of 50 + 55 = 105 students in the fifth grade.

Let the original brine total be x(g), then the salt content is 25%x(g) after adding 10(g) salt, the total salt content is 25%x+10(g), and the total salt water is x+10(g).

According to the title: (25%x+10) (x+10)===>

>==> x=50

Therefore, the original salt content is 50*25%=

If there is x grams of salt, then the salt water x 25% = 4x grams.

x+10）/（4x+10）=

x+10=x+10=x=

The first question is answered correctly, and the second question = 1200 1500 =, that is, a 20% discount.

Let's look at 1 4 first, which is the method of finding a willow leaf.

Two sectors: (square centimeters).

The intersection of the two sectors is the willow leaf shape, that is, the shadow is two layers, one of which is exactly the square with the blank space on both sides, and the remaining part of the square is the willow leaf shadow.

square centimeters) full-picture shadow square centimeters).

Let's look at 1 4 first, which is the method of finding a willow leaf.

Two fan pins: (square centimeters).

The intersection and overlap of the two sectors is the willow leaf shape, that is, the shadow is two layers, one of which and the blank space on both sides just form the positive and withered square, and the rest of the square is the willow leaf shadow.

Defeat height = square centimeters).

Full image shading: square centimeters).

Make a perpendicular line from the right-angled vertex to the bottom edge, because there is an angle of 45 degrees (for an isosceles right-angled triangle), and the vertical line and the bottom edge focus are the midpoints of the bottom edge, so the length of the perpendicular line is 3, s=6x3 2=9

A right triangle with an angle of 45 degrees is an isosceles triangle with a side-to-length ratio of 1:1:2

Because the longest hypotenuse is 6, the two right-angled sides are 6 2 = 3 2

Area = 1 2 * 3 2 * 3 2 = 9

Answer: Since the figure is an isosceles right triangle, set the length of one of the right sides to x.

then there is x 2+x 2 = 36

2x^2=36

x^2=18

Since the area of an isosceles right triangle is s=x*x=18 2=9