Question

A lending library has a fixed charge for the first three days and an additional charge for each day thereafter. Saritha paid ₹27 for a book kept for seven days, while Susy paid ₹21 for the book she kept for five days. Find the fixed charge and the charge for each extra day.​

Answer 1

Answer:  fixed charge = 15,   extra day = 3

Step-by-step explanation:

Let x represent the charge for an extra day (after 3 days)

Let y represent the fixed charge (for first 3 days)

Equation 1:    7 days is 4 extra days   -->      4x + y = 27

Equation 2:   5 days is 2 extra days   -->     2x + y = 21

Multiply the second equation by -1 and add the two equations together:

                   4x + y = 27

                 -2x  - y = -21  

                  2x       =   6

                          x = 3

Input x = 3 into either equation to solve for y:

2x + y = 21

2(3) + y = 21

         y = 15