以下句子是否相等?为什么?Our school is only five minutes' walk from here

以下句子是否相等?为什么?
Our school is only five minutes' walk from here.
=Our school is only a five-minute walk from here.
=Our school is only a five minutes' walk from here.对不?
It's about a five minutes' walk.
=It's about a five-minute walk.
=It's about five minutes' walk.
对不?仔细点!都不同!