This is the 4336th most frequent Arabic word.
مقداره
Its amount or value.
Here, "مقداره" (meaning 'its quantity/extent') is used to indicate the amount or size of the book, which is fifty pages.
اشتريتُ كتابًا مقداره خمسين صفحة.
I bought a book containing fifty pages.
In this sentence, "مقداره" specifies the value or price of a single apple, which amounts to two dollars.
سعر التفاحة الواحدة مقداره دولاران.
The price of one apple is two dollars.
"مقداره" indicates the distance or extent between the two cities, quantified here as one hundred kilometers.