Question

A lending library has a fixed charge for the first three days and an additional charge for each day thereafter.
Mona paid ₹27 for a book kept for 7 days, while Tanvy paid ₹21 for the book she kept for 5 days.
Find the fixed charge and the charge for each extra day.

Answer 1

Let the fixed charge be ₹x and the charge for each extra day be ₹y.
In case of Mona, as per the question
$x+4y=27.....\left(i\right)$
In case of Tanvy, as per the question
$x+2y=21.....\left(ii\right)$
Subtracting (ii) from (i), we get
$2y=6\Rightarrow y=3$
Now, putting y = 3 in (ii), we have
$$\begin{gathered} x+2\times 3=21 \\ \Rightarrow x=21-6=15 \end{gathered}$$
Hence, the fixed charge be ₹15 and the charge for each extra day is ₹3.