To round 2543 to the nearest ten you need to look at the numbers, we round the number UP to the nearest ten if the last digit in the number is 5, 6, 7, 8, or 9.We round the number DOWN to the nearest ten if the last digit in the number is 1, 2, 3, or 4.To remember this rule I think of little rhymes, for example: "5 to nine climb the vine, 0 to four slide to the floor!".Also If the last digit is 0, then we do not have to round anything, because it is already to the ten. So the answer is 2540, Hope this helps!