A kind of children's story book was delivered to the bookstore, which sold 30% in the first day, sold 120% in the second day, and bought 30 more in the first day. How many children's story books were delivered to the bookstore What's the point

A kind of children's story book was delivered to the bookstore, which sold 30% in the first day, sold 120% in the second day, and bought 30 more in the first day. How many children's story books were delivered to the bookstore What's the point

The next day they sold 120% of what they bought the first day, so they sold the next day:
30%x120%=42%
More than the first day:
42%-30%=12%
So there are:
30 △ 12% = 250 (this)

A kind of children's story book was delivered to the bookstore. It sold 30% on the first day, and 120% on the second day, 30 more than the first day. How many of these story books were delivered to the bookstore?

30% × 120% - 30%, = 30% × 6%, = 500 copies; a: there are 500 copies of this kind of story books from the bookstore

Don't use unknowns to work out this problem. The bookstore sent a batch of story books. On the first day, they sold 15 bags less than one sixth of these books. There are still 》
Don't use unknowns to work out the problem. A batch of story books were sent to the bookstore. On the first day, they sold 15 bags less than one sixth of these books. There are still seven eighths left. How many bags are there in this batch of story books

What's sold
1－7/8=1/8
At the same time, it's 15 bags less than 1 / 6
therefore
What are the characteristics of these storybooks
15 ÷ (1 / 6-1 / 8) = 360 (package)

The perimeter of two similar triangles is 15 cm and 20 cm respectively, and the area sum is 25 square cm. What is the area of the larger triangle?

The similarity ratio is 15:20 = 3:4
The area ratio is: 3 & # 178;: 4 & # 178; = 9:16
The larger area is: 25 × 16 / (16 + 9) = 16 square centimeters

3 8 15 24 general term formula

1 × 3 = 3, 2 × 4 = 8, 3 × 5 = 15, 4 × 6 = 24, the general formula a (n) = n (n + 2), n is greater than or equal to 1
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For a trapezoid, if the bottom and height remain unchanged and the upper bottom increases by 0.6, the area will increase by 1.2 square meters. What is the area of the trapezoid?

Area of trapezoid = 1 / 2 (upper bottom + lower bottom) × height
The area of trapezoid is increased by 1 / 2 × 0.6 × height = 1.2 with the increase of 0.6 in the top and bottom
So the height of the trapezoid is 4 meters

How to solve the equation x-20 = x / 12

X-X/12=20
11X/12=20
X=240/11

The bottom of a triangular piece of glass is 10 decimeters, and the height is 6 decimeters. How much does this piece of glass cost according to 40 yuan per square meter?

10 * 6 / 2 = 30 square decimeter = 0.3 square meter
40 * 0.3 = 12 yuan

-What is the sum of the first 99 consecutive integers in the string of 49, - 48, - 47... 2009

50

In isosceles △ ABC, the median line BD on one waist AC divides the circumference of △ ABC into two parts, 12cm and 15cm, and calculates the length of each side of △ ABC

As shown in the figure, ∵ BD is the middle line, ∵ 12cm is the sum of waist length and half of waist length, waist length = 12 △ 1.5 = 8cm, bottom edge = 15-8 × 12 = 11cm, three sides of triangle are 8cm, 8cm and 11cm respectively, which can form triangle. When 15cm is the sum of waist length and half of waist length, waist length = 15 △ 1.5 = 10cm, bottom edge = 12-10 × 12 =