Question

Which is closest to 0.5? 0.4, 0.505, 0.449, 0.48 or 0.53?

Answer 1

Let us calculate the nearness of all the numbers provided
Number        Nearnes
0.400                100
0.505                   5
0.449                  51
0.530                30

Thus 0.505 is the closest number to 0.5 in decimal terms

Answer 2

$1)|0.5-0.4|=0.1\\ 2)|0.5-0.505|=0.005\\ 3)|0.5-0.48|=0.02\\ 4)|0.5-0.53|=0.03$

As you see the seconds difference is the smallest therefore 0.505 is closest to .0.5