课时训练·基础达标
7、30
8、75
9、解:∵ a = 2 cm,b = 30 m = 3 000 cm,c = 6 cm,d = 10 m = 1 000cm,
∴ a < c < d < b.
∵ a/c = 2/6 = 1/3 ,d/b = 1 000/3 000 = 1/3
∴ a/c = d/b
∴ 它们是成比例线段.
10、解:(1)由已知,得MN = AB ,MD = 1/2AD = 1/2BC.
∵ 矩形DMNC与矩形ABCD相似,
∴ DM/AB = MN/BC,即1/2 AD² = AB²,由AB = 4得,
(2)矩形DMNC与矩形ABCD的相似比为