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The roller of a roller is 10 meters long and 0.8 meters in diameter. If it rolls 20 times, how many meters will it advance? What is the area of the road surface?
3.14 × 0.8 × 20 = 50.24 (meters); 3.14 × 0.8 × 10 × 20 = 25.12 × 20 = 502.4 (square meters); answer: turn 20 weeks to advance 50.24 meters, the area of roller is 502.4 square meters
1. (1) someone uses a 7.5 meter long wall as one side and a 13 meter long bamboo fence as the other three sides to form a rectangular vegetable garden with an area of 20 square meters. What is the length and width of the rectangular vegetable garden?
(2) In other conditions, can we change the length of the square wall to 1.5 meters?
(3) In question (1), if you want to build a rectangular vegetable garden with an area of 22.5 square meters, can you do it?
Now it's time
(1) Let the length of the wall be x (x)
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