How do you measure exactly 1 litre bu using a 7 litres jar and a 9 litres jar?
Fill the 7L (7L, 0L),Pour from 7L to 9L (0L, 7L),Refill the 7L (7L, 7L),Pour from 7L to 9L (5L, 9L),Empty 9L (5L, 0L),Pour from 7L to 9L (0L, 5L),Refill the 7L (7L, 5L),Pour from 7L to 9L (3L, 9L),Empty 9L (3L, 0L),Pour from 7L to 9L (0L, 3L),Refill the 7L (7L, 3L),Pour from 7L to 9L (1L, 9L).Done!