I have similar way of calculating square meters from square feet. "Subtract 10% divide by 10". So for example 900 square feet: 900 - 90 = 810/10 = 81. Real answ

I have similar way of calculating square meters from square feet. "Subtract 10% divide by 10". So for example 900 square feet: 900 - 90 = 810/10 = 81. Real answer is 83.6, close enough for me.