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 70 is 15 (70 - 55 = 15).

Next, we need to find the average of the two numbers. The average of 55 and 70 is (55 + 70) / 2 = 62.5.

Now, we can find the percentage difference by dividing the absolute difference by the average and multiplying by 100. So, the percentage difference between 55 and 70 is (15 / 62.5) x 100 = 24%.

This means that the second number (70) is 24% higher than the first number (55).