Question

A certain bacterial culture is multiplying in a culture dish, doubling in size every 6 minutes. It takes exactly an hour to fill the whole dish. How long does it take to fill half the dish?

Answer 1

doubling in size,

if the whole dish is filled in an hour (all of it)
how long does it take to fill 1/2 dish?

notice that
1/2 doubled=1/2 times 2=2/2=1 whole dish
therefor it only doubled one more time from the 1/2 point

1hour=all
1hour-6mins=1/2 dish

1hour-6mins=60-6=54 minutes


answer is 54 minutes