Here is a puzzle that you could ask.
You have got a 7 Gallons jar and a 12 Gallons jar you have to measure exactly 3 Gallons and put it in a radiator

you have ample water supply but no third jar and no markings allowed on the jars


This is one possible solution.
here u go...

0 0 (start)
0 12 (fill 12 gallon jar)
7 5 (transfer 7 gallon from 12 gallon jar)
0 5 (empty 7 gallon jar)
5 0 (transfer 5 gallon to 7 gallon jar)
5 12 (fill 12 gallon jar again)
7 10 (transfer 2 gallon to 7 gallon jar)
0 10 (empty 7 gallon jar again)
7 3 (transfer 7 gallon to 7 gallon jar)
remaining 3 gallon in 12 gallon jar...