The number 4.9 is greater than 4.09 by 0.81.
This problem can be solved using two methods:
First method: Subtract the small number from the greater one.
[tex]4.9-4.09=0.81[/tex]
Second method: Subtract both numbers in any order and take the absolute value:
[tex]1. \ \mid 4.09 - 4.9 \mid = \mid -0.81 \mid =0.81 \\ \\ 2. \ \mid 4.9 - 4.09 \mid = \mid 0.81 \mid =0.81[/tex]