The actual difference = 55 − 52 = 3 miles. Now we want to convert this into percentages. For this note that the error in miles is corresponding to 55 km. i.e. 3 per 55.

Let x% denote the required percent. Then we have

 x% of 55 = 3

 x/100 × 55 = 3

 x = (3 × 100)/55 = 5.45

Therefore, the percentage correct to two decimal places is 5.45%.