Greetings!
First off, we should know that there are 60 minutes in an hour. Therefore, the first step we will need to do, is divide 60 by 10.
60 ÷ 10 = 6
As shown above, we now know we will have to double the number 6 times. If we start with 30, this will be our first problem.
(1) 30 + 30 = 60
And so on and so forth...
(2) 60 + 60 = 120
(3) 120 + 120 = 240
(4) 240 + 240 = 480
(5) 480 + 480 = 960
(6) 960 + 960 = 1920
And after our sixth time we have our answer:
1920 bacteria
Hope this helps!
~Fluerie