Puzzle

CA Bharat kumar (Practice) (622 Points)

11 February 2013  

Dear Friends

I would like to ask one puzzle which is simple if you are good in mathematics.

When there are no watches in this world, there is a siant who worshipping lord Kali from decades to get a wish.

On one fine day in order to test his 'Bhakti' 'Lord Kali' speaks from the idol and say like this:

My dear saint i was impressed with your bhakti and you have to finish one pooja to get your wishes and gave him two sand watches one(Small) calculates 4 min of time and the other(big) calculates 7 min of time and you should complete this pooja in exact 9 minutes.

Saint started pooja and completed in 9 min by using the both sand watches.

How the saint used them?