An additional to a house increases the floor area from 275m² to 300m². By what percent was the original floor area increased?

25/275 = 0.09 = 9%

Why do you divide by 25?

300 - 275 = 25

To find out the percentage increase in the original floor area, we can follow these steps:

1. Calculate the difference in floor areas: New floor area - Original floor area
Difference = 300m² - 275m² = 25m²

2. Determine the percentage increase: (Difference / Original floor area) x 100%
Percentage Increase = (25m² / 275m²) x 100%

Now, let's simplify this equation:
Percentage Increase = (25/275) x 100%
Percentage Increase = (1/11) x 100%
Percentage Increase = 9%

Therefore, the original floor area was increased by 9%.