Question

Measure 1 to 40 litres using only four cans? There is a drum full of milk, people come for buying milk in the range of 1-40 litres. You can have only 4 cans to draw milk out of drum. What should be the measurement of these four cans so that you can measure any amount of milk in the range of 1 to 40.

Answer 1

the cans you would use should be 1,3,9,27
for measuring anything between 1-40L they should suffice

Logic:
1,3 can get anything from 1 to 4 (1, 3-1, 3, 3+1)
put in the 9 and you can get anything from 5 to 13 (9-(1 to 4), 9+(1 to 4))
put in the 27 and you can get anything from 14 to 40 (27 - (1 to 13), 27 + (1 to 13))

Answer 2

Answer:

1, 3, 9, 27

Step-by-step explanation:

If we have a can of 1 litre then the range that we can measure: [1, 1]

If we have cans of 1 litre and 3 litres then the range that we can measure: [1, 4] = { 1, 3–1, 3, 3+1 }

How to choose the next can to have: 2*(high of last range) + 1 = 2*4+1 = 9

( Verify it why we choose 3 litres can last time )

So, If we have cans: 1, 3, 9 then the measurable range: [1, 13] = { 9 - [1, 4] , 9 + [1, 4] }

If we have cans: 1, 3, 9, 27 (i.e. 2*13+1) then the range: [1, 27+13] = [1, 40]