To find the percentage difference between two numbers, we first need to find the absolute difference between them. In this case, the absolute difference between 55 and 34 is 21 (55-34=21).

Next, we need to find the average of the two numbers. The average of 55 and 34 is (55+34)/2 = 44.5.

Now, we can calculate the percentage difference by dividing the absolute difference by the average and multiplying by 100. So, the percentage difference between 55 and 34 is (21/44.5) x 100 = 47.19%.

Therefore, the percentage difference between 55 and 34 is 47.19%. This means that the difference between 55 and 34 is almost half of the average of the two numbers.