There is one drum full of milk and people come to buy milk in a range of 1-40 litres. You only have 4 cans to draw milk out of the drum. What should be the measurement of the 4 cans so that you can measure any amount of milk in the range of 1-40 litres?
What is the sum of all 4 digit numbers that can be formed by the digits 0, 1, 2, 3, 4? No repetitions allowed.