11. The side of a square are all decrease
by 1% by what percent is the area
decreased ?

By 19 percent

Explanation:

Lets take a square that has the side length 10. The area of this square is obviously 100. Now let's decrease the side length by 1% making the new side length 9. the area of this new square is 9x9 = 81. Now let's find the percentage:

(81/100) × 100% = 81%. this is the percent of area the new square is of the old one

100-81 = 19

i-i-i-i-i-i don't k-k-k-k-know.