The classroom is 80 meters long, 60 meters wide, 25 meters high, with 180 square meters of doors and windows. The ceiling and four walls of the classroom need painting. It costs 15 yuan per square meter; How much does it cost to paint the whole classroom?

The classroom is 80 meters long, 60 meters wide, 25 meters high, with 180 square meters of doors and windows. The ceiling and four walls of the classroom need painting. It costs 15 yuan per square meter; How much does it cost to paint the whole classroom?

First calculate the area of the whole classroom
80 * 25 * 2 (area of two walls on both sides) + 60 * 25 * 2 (area of front and back walls) + 80 * 60 (ceiling area) = 11800 square meters
Total area minus the area of doors and windows:
11800 -- 180 = 11620 square meters
So: the cost of painting the whole classroom is: 11620 * 15 = 174300 yuan

The school conference room is 15 meters long and 8 meters wide. How fast does it take to lay 4-decimeter-long floor tiles for the conference room?

4 decimeters = 0.4 meters
Area of a tile: 0.4 × 0.4 = 0.16 (M2)
Area of conference room: 15 × 8 = 120 (M2)
Number of tiles required: 120 △ 0.16 = 750
A: a total of 750 yuan

The top of the granary is cylindrical. The perimeter of the ground is 36 meters, and the bus is 8 meters long. How many linoleum are there in the street, 10% of the linoleum materials needed to be laid to prevent rain
The top of the granary is cylindrical, the perimeter of the ground is 36m, and the bus is 8m long. In order to prevent rain, it is necessary to lay 10% of the linoleum materials. How much linoleum should be used for joints

It is to calculate the surface area of the cylinder - the bottom area (the bottom does not need to be covered with linoleum) = the side area + the bottom area
Diameter = perimeter △ Π = 36 / Π (m),
Radius = diameter △ 2 = 36 / Π 2 = 18 / Π (m)
Bottom area = radius × radius ×Π = 18 / Π × 18 / Π×Π = 324 / Π (M2),
Side area = perimeter × bus length = 36 × 8 = 288 (M2),
324/∏+288+(324/∏+288)×10%
=324÷3.14+288+(324÷3.14+288)×10%
=391.18+39.12
=430.30 (M2)