Total no. Of products that is bought by store = 2000

Price of one product= 10 rs

Then the total cost of all products will be = 2000*10 = 20000

Now-

Store sold 100 products at 15rs –

Then earn = 100*15 = 1500

And

Sold 20 products at 20rs –

Then earn = 20*20 = 400

Total earning = 1500 + 400 = 1900

We know –

loss/profit = total revenue – total cost

Loss/profit = 1900 – 20000= -18100

Mean store are in loss with ( – 18100) rs…

Then

Percentage of loss = ( loss/toal cost)*100

Percentage of loss = (-18100/20000) = -90.5

Then Total percentage of loss will be -90.5