$ perl -e'printf qq[%s => %.68f => %.1f\n], (qq[0.${_}5]) x 3 for (0..9)' 0.05 => 0.05000000000000000000067762635780344027125465800054371356964111328125 => 0.1 0.15 => 0.15000000000000000000542101086242752217003726400434970855712890625000 => 0.2 0.25 => 0.25000000000000000000000000000000000000000000000000000000000000000000 => 0.2 0.35 => 0.34999999999999999999457898913757247782996273599565029144287109375000 => 0.3 0.45 => 0.44999999999999999998915797827514495565992547199130058288574218750000 => 0.4 0.55 => 0.55000000000000000001084202172485504434007452800869941711425781250000 => 0.6 0.65 => 0.64999999999999999997831595655028991131985094398260116577148437500000 => 0.6 0.75 => 0.75000000000000000000000000000000000000000000000000000000000000000000 => 0.8 0.85 => 0.85000000000000000002168404344971008868014905601739883422851562500000 => 0.9 0.95 => 0.94999999999999999998915797827514495565992547199130058288574218750000 => 0.9