You are given an array rectangles containing $n$ rectangles, where rectangles[i] = $[ ext{width}_i, ext{height}_i]$ represents the dimensions of the $i^{ ext{th}}$ rectangle.

Two rectangles $i$ and $j$ (where $i < j$) are considered interchangeable if they have the same width to height ratio, defined as $\frac{ ext{width}_i}{ ext{height}_i} = \frac{ ext{width}_j}{ ext{height}_j}$.

Return the total number of interchangeable pairs of rectangles in rectangles.

Constraints:

• $n =$ rectangles.length

• $1 \leq n \leq 10^5$

• rectangles[i].length $= 2$

• $1 \leq ext{width}_i, ext{height}_i \leq 10^5$

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