The number of bacteria in a petri dish doubles every 5 hours. If there were originally 4 bacteria in the petri dish, after how many hours, to the nearest tenth of an hour, would it take to reach 1000 bacteria?
number = 4(2^(t/5) )
1000 = 4 (2^(t/5))
250 = 2^(t/5)
take logs of both sides and apply the rules for logs
log 250 = (t/5) log 2
t/5 = log250/log2 = 7.96578..
t = 39.8 hours