.
the maximum number of Math workbooks you can buy is the greatest integer number which is less or equal to
= use your calculator = 21.9.
which gives the ANSWER of 21 Math books.
Solved.
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Actually, such SUPER-simple problems deserve to be solved in one line,
because their solution is absolutely clear, simple and obvious.
Also, in such problems, it is absolutely unnecessary to write two zeroes after the decimal point,
since it ONLY distracts an attention and has no any rational sense.