HOW MUCH DID HE DRINK ?

To conserve the contents of a 16 oz. bottle of tonic, a castaway adopts the following procedure. On the first day he drinks 1 oz. of tonic and then refills the bottle with water; on the second day he drinks 2 oz. of the mixture and then refills the bottle with water; on the third day he drinks 3 oz. of the mixture and again refills the bottle with water. The procedure is continued for succeeding days until the bottle is empty. How many ounces of water does he thus drink?

Solution...

Let the entire content of tonic (16 oz.) to be x

1st Day == x-1+1 ==

"

"

15th Day = x-15+15

16th Day = x-16 == 0 (No more refill)

So how much does he drink ??

My solution is that he drink 136 oz. of tonic.

(1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 = 135) oz.