5.8 x 2.19
= (5.00 + 0.80) x (2.00 + 0.19)
= 5.002.00 + 5.000.19 + 0.802.00 + 0.800.19
= 10.00 + 0.95 + 1.60 + 8/10 19/100
= 10.00 + 0.95 + 1.60 + (8(10+9))/1000
= 10.00 + 0.95 + 1.60 + (80+72)/1000
= 10.00 + 0.95 + 1.60 + 152/1000
= 10.000 + 0.950 + 1.600 + 0.152
= 11.600 + 0.950 + 0.152
= 12.550 + 0.152
= 12.702
It actually is a reasonable value.