Question 1090781
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A combination of (1 big book plus 4 small books) costs exactly 5 dollars and contains 5 books.


So, 10 times this combination satisfies/satisfy to the condition.


<U>Answer</U>. 10 big books and 4*10 = 40 small books.
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I was lasy to write and to solve the problem using the system of equations.
So, I solved it <U>MENTALLY</U>, instead.