02-11-2010, 03:26 PM
hi (freaking #s .i hate'm)
10 raise to the power of 9. just put nine "0" in front of "1"
1,000,000,000 ( # of bacterias)
every time we knock off a "0" we are left with the 10% (90% bacterias killed)= takes 10 minutes
in 80 minutes we knock off eight"0" and we are left with 10 bacterias.
so to knock off nine "0" it will take us 90 minutes and we'll be left with 1 bacteria and since 90 is not the choice and 100 minutes is the shortest amount of time listed to bring the # of bacterias below 10, that would be the answer.
good luck
10 raise to the power of 9. just put nine "0" in front of "1"
1,000,000,000 ( # of bacterias)
every time we knock off a "0" we are left with the 10% (90% bacterias killed)= takes 10 minutes
in 80 minutes we knock off eight"0" and we are left with 10 bacterias.
so to knock off nine "0" it will take us 90 minutes and we'll be left with 1 bacteria and since 90 is not the choice and 100 minutes is the shortest amount of time listed to bring the # of bacterias below 10, that would be the answer.
good luck