ANSWER
The Percentage decrease is
[tex]45\%[/tex]
EXPLANATION
The initial value
[tex]20 \: miles[/tex]
The final value
[tex] = 11 \: miles[/tex]
The percentage decrease can be calculated using the formula,
[tex]Percentage \: decrease \: = \frac{final \: value - inital \: value}{initial \: value} \times 100\%[/tex]
We substitute the values to obtain,
[tex]Percentage \: decrease \: = \frac{11 - 20}{20} \times 100\%[/tex]
This will simplify to,
[tex]Percentage \: decrease \: = \frac{ - 9}{1} \times 5\%[/tex]
[tex]Percentage \: decrease \: = - 45\%[/tex]
The negative sign is just there to indicate decrement.
Therefore the percentage decrease is
[tex]45\%[/tex]
