When the price of an article was reduce by 20%, its sale increased by 80%. What was the net effect on the sale ?

Let conside 100 item sold on Rs.100
∴ Total Amount = 100 × 100 = Rs. 10000
Now After 20% discount price become Rs.80
Total Number of Sale increased after discount is 80%.
i.e.
100 + 80% of 100 = 180(Item sold)
∴ Total Amount = 180 × 80 = Rs. 14400

Increased in amount = 14400 - 10000 = 4400
% Increase in amount
= $$\frac{{4400 \times 100}}{{10000}} $$
= 44% (increase)