The number of bacteria in a colony was growing exponentially. At 4 pm yesterday the number of bacteria was 400 and at 6pm yesterday it was 3600. Howmany bacteria were there in the colony at 7 pm yesterday?
a.3600
b.10800
c.32400
d.14400

• growing exponentially.so at 4p.m.it is 400...and at 5 p.m it is 400*3=1200,and at 6p.m it is 1200*3=3600, and at 7p.m.it shuld be 3600*3=10800
• 13 years agoHelpfull: Yes(32) No(2)
• at 4pm ,no. of bacteria =400
  and it is incresed exponentialy...
  at 6pm,no. of bacteria=3600
  3600/400 = 9 = 3^2,for 2 hours
  at 7pm,which means 3 hours later,
  no. of bacteria = 400 X 3^3 = 400 X 27 = 10800
  which is option B
• 13 years agoHelpfull: Yes(18) No(0)
• At 4 pm no. of bacteria=400
  and it increased exponentially
  them after 1 hour(at 5pm) increased bacteria = (400*4)/2=800
  and total bacteria after 1 hour = 800+400 = 1200
  and again after 1 hour (at 6pm) increased bacteria = (1200*4)/2=2400
  and total bacteria = 2400 + 1200= 3600 (as given in question)
  then at 7 pm(after 1 hour again) increased bacteria is= ( 3600*4)/2= 7200
  and total bacteria at 7pm is= 7200 + 3600 =10800
  and answer B is correct
• 13 years agoHelpfull: Yes(8) No(2)
• here at 4pm no of bacteria is 400, after 2 hours at 6pm it is 3600. since in 1 hour at 5pm it is 3 times i.e,400*3=1200 and in next 1 hour at 6pm it is again 3 times i.e,1200*3= 3600, then at 7pm it will be 3600*3=10800
  So the answer is b. 10800
• 13 years agoHelpfull: Yes(5) No(0)
• given dat 3600=400 exp(rate*time)....time is 2 hrs...find rate by using log....
  then the ans cn b solved using the same equation...u kno d rate and time=3 hr....ans is 10800
• 13 years agoHelpfull: Yes(3) No(5)
• Answer is 14400.
  At 4 pm no of bacteria = 400.
  At 6 pm no of bacteria = 3600. (9 * 400 )(It increases at rate of 9 per 2 hours)
  At 8 pm no of bacteria = 32400.(9 * 3600)
  At 4 pm no of bacteria = 14400.
  (7pm)=(8pm-6pm)/2
  =>(32400-3600)/2
  => 28800/2
  =14400.
  
• 13 years agoHelpfull: Yes(1) No(15)