How do I use grid with percentage width

Questions
1

I am trying to create two columns where one of them takes x% of the page (and the other column fills the rest) using grid:

#grid(
    columns: (30%,70%), align: center,
    [Content A],
    [Content B]
)

What I also tried was:

#grid(
    columns: (1fr,3fr), align: center,
    [Content A],
    [Content B]
)
2

The second example created the desired result. I didn’t notice it already worked:

#grid(
    columns: (2fr,1fr), align: center,
    [Content A],
    [Content B]
)

image
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