The volume of sales in the first year decreased by some amount, and in the second year it decreased by three times.

The volume of sales in the first year decreased by some amount, and in the second year it decreased by three times. as a result, over 2 years the volume of sales decreased by 80%. By what percentage has sales decreased each year?

1) 100% – 80% = 20 (%) left after 2 years.

2) 20%: 100% = 0.2 (part) left after 2 years.

The initial sales volume was equal to “1” -th integer part.

Let for the 1st year this volume fell by a part equal to “x”.

Then for the 2nd year the same volume fell by another part equal to “3x”.

Knowing that in the end 0.2 part of the volume remained, we will draw up an equation.

1 – x – 3x = 0.2;

-4x = 0.2 – 1;

-4x = -0.8;

x = 0.8: 4;

x = 0.2 (part) decreased in the 1st year.

3) 0.2 * 100% = 20 (%) decreased in the 1st year.

4) 3x = 3 * 0.2 = 0.6 (part) decreased in the 2nd year.

5) 0.6 * 100% = 60 (%) decreased in the 2nd year.