Tom sold a phone for Rs.4500 at a loss of 20%. What is the Cost Price of the phone?

Selling Price = Rs.4500

Loss % = 20%

Let the CP be 100, 20% of 100 = 20

So , S.P. = 100 – 20 = Rs. 80

If the CP is Rs. 100, then the SP is Rs. 80

If the CP is Rs. x, the SP is Rs. 4500.

Hence by unitary method,

Hence x =$\frac{4500 \times 100}{80}$

         = Rs.5625