To pave a classroom with floor tiles, if you use square bricks with a side length of 5 decimeters, you need to use 38 bricks. If you want to pave 20 square bricks, how many decimeters**2 square bricks should be used instead?
要用地砖铺一间教室，如果用边长是5分米的方砖铺，要用38块，如果要铺方砖20块，应改用多少分米**2的方砖？
<result>47.5</result>