USA SIZE

Im assuming without a calculator;

well - lets turn ${3.806}^{2}$

into ${(x+0.806)}^{2}$ where $x=3$

now we expand $x^2 +2(0.806)+{(0.806)}^{2}$

0.806$\times$0.806 is much easier to do than 3.806^2

$0.806\times0.806 =$

2((0.806 * 0.400)+(0.806 * 0.003))

2((0.32+0.0024)+(0.002418))

2(0.3224+0.002418)

2(0.324818)

0.649636

$x^2+2(0.806)+0.649636$

sub $x=3$

$(3)^2+2(0.806)+0.649636$

$9+1.612+0.649636$

$11.261636$

ta dah!