alinazubairx
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#1
Report Thread starter 1 year ago
#1
this question i came across: does anyone know how to do it?
Legionnaires’ disease is a serious lung infection caused by Legionella bacteria.
In 2015 there were 18 confirmed cases of Legionnaires’ disease in Wales. The population
of Wales in 2015 was 3099100.
During an outbreak, a sample of contaminated water was studied to find which antibiotic was
most effective. The three antibiotics were erythromycin, ciprofloxacin and azithromycin. A
range of concentrations of each antibiotic were used.
A microbiologist carried out the investigation as follows:
▪ Sterile nutrient agar plates were set up containing different concentrations of
erythromycin.
▪ 0.5cm3 of diluted contaminated water was transferred onto each plate.
▪ The same process was repeated for ciprofloxacin and azithromycin.

(i) The microbiologist had diluted the original sample of contaminated water by a factor
of 10–3. Use the information given to calculate the number of Legionella bacteria in
1cm3 of the original contaminated sample. Show your working. [2]
Last edited by alinazubairx; 1 year ago
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sarahjanesmith
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#2
Report 1 year ago
#2
(Original post by alinazubairx)
this question i came across: does anyone know how to do it?
Legionnaires’ disease is a serious lung infection caused by Legionella bacteria.
In 2015 there were 18 confirmed cases of Legionnaires’ disease in Wales. The population
of Wales in 2015 was 3099100.
During an outbreak, a sample of contaminated water was studied to find which antibiotic was
most effective. The three antibiotics were erythromycin, ciprofloxacin and azithromycin. A
range of concentrations of each antibiotic were used.
A microbiologist carried out the investigation as follows:
▪ Sterile nutrient agar plates were set up containing different concentrations of
erythromycin.
▪ 0.5cm3 of diluted contaminated water was transferred onto each plate.
▪ The same process was repeated for ciprofloxacin and azithromycin.

(i) The microbiologist had diluted the original sample of contaminated water by a factor
of 10–3. Use the information given to calculate the number of Legionella bacteria in
1cm3 of the original contaminated sample. Show your working. [2]
is there not a table for this question?
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sarahjanesmith
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#3
Report 1 year ago
#3
(Original post by alinazubairx)
this question i came across: does anyone know how to do it?
Legionnaires’ disease is a serious lung infection caused by Legionella bacteria.
In 2015 there were 18 confirmed cases of Legionnaires’ disease in Wales. The population
of Wales in 2015 was 3099100.
During an outbreak, a sample of contaminated water was studied to find which antibiotic was
most effective. The three antibiotics were erythromycin, ciprofloxacin and azithromycin. A
range of concentrations of each antibiotic were used.
A microbiologist carried out the investigation as follows:
▪ Sterile nutrient agar plates were set up containing different concentrations of
erythromycin.
▪ 0.5cm3 of diluted contaminated water was transferred onto each plate.
▪ The same process was repeated for ciprofloxacin and azithromycin.

(i) The microbiologist had diluted the original sample of contaminated water by a factor
of 10–3. Use the information given to calculate the number of Legionella bacteria in
1cm3 of the original contaminated sample. Show your working. [2]
i tried looking for the mark scheme, but i couldn't find it. sorry
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alinazubairx
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#4
Report Thread starter 1 year ago
#4
(Original post by dingding123)
is there not a table for this question?
there is yeah. hold on let me link the paper:
https://pmt.physicsandmathstutor.com...%20A-level.pdf
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sarahjanesmith
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#5
Report 1 year ago
#5
(Original post by alinazubairx)
there is yeah. hold on let me link the paper:
https://pmt.physicsandmathstutor.com...%20A-level.pdf
the answer would be
86000x 2
so it would be 172000
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alinazubairx
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#6
Report Thread starter 1 year ago
#6
(Original post by dingding123)
the answer would be
86000x 2
so it would be 172000
why do u do that? multiply 86000 by 2?
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Cat b
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#7
Report 1 year ago
#7
How can I improve on application question I do aqa bio
I’ve done so many exam practice questions n I’m not improving much n hv exams tomorrow help!
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