A type of bacteria doubles in number every 12 hours. After 2 days, there are 48 bacteria. How many bacteria were there at the beginning of the first day.

I know the answer is 3, but want to know how it arrived at the number "3"

2 answers

work backwards
since they "doubled" every 12 hours ...
(1/2 day = 12 hours)

at end of 2 days -- 48
at end of 1.5 days -- 24
at end of 1 day -- 12
at end of 1/2 day -- 6
at start ----------- 3
No the right answer