If you change the order of these digits you can get 24 different numbers, for example 2547, 2574, 2745, … Can you find all 24 different numbers made by using each of the digits 2, 4, 5, 7 just once?
How many of these numbers have 2 in the thousands place? How many have 2 in the hundreds place? How many have 2 in the tens place? How many have 2 in the units place?
Now find what these 24 four digit numbers add up to.
How many methods can you find for solving this problem?
See the NRICH website for this and similar problems.