You have 2 sand box in hand. One sand box will measure the 7 minsanother one will measure 4 mins.Using this two sand box you need measure 9 mins. In butween you want stop the filling sand from top to bottom or bottom to top you can do.
You have 2 sand box in hand. One sand box will measure the 7 minsanother one will measure 4 mins.Using this two sand box you need measure 9 mins. In butween you want stop the filling sand from top to bottom or bottom to top you can do.
