If a room is paved with 30 cm long square bricks, 800 pieces are needed. If a room is paved with 50 cm long square bricks, how many pieces are needed? (solve by proportion)

If a room is paved with 30 cm long square bricks, 800 pieces are needed. If a room is paved with 50 cm long square bricks, how many pieces are needed? (solve by proportion)

Let x block be required, 30 × 30 × 800 = 50 × 50 × X & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2500x = 900 × 800 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2500x = 720000 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 288 A: 288 blocks are required

If a room is paved with 30 cm long square bricks, 800 pieces are needed. If it is paved with 25 square decimeters square bricks, how many pieces are needed
There is a proportional response

Original area = 30 × 30 = 900 square centimeter = 9 decimeter
Need = 800 × 9 △ 25 = 288 pieces

If a room is paved with 30 cm long square bricks, 800 pieces are needed. If a room is paved with 50 cm long square bricks, how many pieces are needed? (solve by proportion)

Let x block be required, 30 × 30 × 800 = 50 × 50 × X & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2500x = 900 × 800 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2500x = 720000 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 288 A: 288 blocks are required

Xiaoming's room is 6 meters long and 4 meters wide. Now it needs to be paved with square bricks. The market has square bricks with an area of 16 square decimeters
It's 5 yuan each. The square brick with an area of 25 square decimeters is 7.5 yuan each. What kind of square brick do you think the Xiaoming family should buy? How much does it cost? I'm so anxious!

4 × 6 = 24 (square meter) = 2400 (square decimeter)
2400 △ 16 = 150 (pieces)
150 × 5 = 750 yuan
2400 △ 25 = 92 (pieces)
92 × 7.5 = 690 yuan
A: you should buy square bricks with an area of 25 square decimeters, which costs 690 yuan