You want to know how long it'll take for the bacteria to grow
to (800/500) = 1.6 times their initial population.
The number of double-times it'll take is
[ log(1.6) / (log(2) ] = 0.6781 .
The double-time for these particular critters is 12 hours,
so it'll take them
0.6781 x 12 hours = 8.137 hours
= 8 hours 8.2 minutes .
Greatest common factor (GCF) of 12 and 21 is 3. We will now calculate the prime factors of 12 and 21, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 12 and 21.