Why does multiplying by 1.1 add 10 percent of the area?

Multiplying by 1.1 increases a quantity by 10 percent because 1.1 represents the original amount (100%) plus an additional 10% of that amount. When applied to an area, this means that the new area is equal to the original area plus 10% of the original area. This results in a total area that is 110% of the original, effectively adding 10 percent to it. Thus, multiplying by 1.1 directly scales the area up by 10 percent.