To find the percentage difference between two numbers, we first need to calculate the absolute difference between them. In this case, the absolute difference between 375 and 400 is 25.

Next, we need to find the average of the two numbers. The average of 375 and 400 is (375+400)/2 = 387.5.

Now, we can calculate the percentage difference by dividing the absolute difference by the average and multiplying by 100. So, the percentage difference between 375 and 400 is (25/387.5) x 100 = 6.45%.

Therefore, the percentage difference between 375 and 400 is 6.45%. This means that 400 is 6.45% greater than 375.