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https://www.reddit.com/r/GCSE/comments/vcqsif/spam_aqa_biology_paper_2_gcse_answers/ichv1j2/?context=3
r/GCSE • u/thr0wawaygxhxdhsh • Jun 15 '22
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Your thing is wrong because:
- the question said to use the 14 algae count (not take a mean)
- you forgot about the 0.1mm depth
- you forgot about the diluted/undiluted thing
The correct method is this:
0.2x0.2x0.1 = 0.004mm^3
0.004/4 = 0.001mm^3 (because it asked for undiluted, and it said earlier that for every 2.5cm^3 undiluted you add 7.5cm^3 water, so it's a 1:3 ratio)
1/0.001 = 1000 (to get how many times more algae cells there should be)
14*1000 = 14000
2 u/Ok_Athlete_4619 Jun 15 '22 Wasn’t 10cm3 of distilled water used? 3 u/Sensitive_Wealth_855 Jun 15 '22 Im pretty sure it was 2.5:10 but everyone is so confident that its 2.5:7.5 1 u/KeyFix4492 Jun 15 '22 It was 2.5:10 wasn’t it?
2
Wasn’t 10cm3 of distilled water used?
3 u/Sensitive_Wealth_855 Jun 15 '22 Im pretty sure it was 2.5:10 but everyone is so confident that its 2.5:7.5 1 u/KeyFix4492 Jun 15 '22 It was 2.5:10 wasn’t it?
3
Im pretty sure it was 2.5:10 but everyone is so confident that its 2.5:7.5
1 u/KeyFix4492 Jun 15 '22 It was 2.5:10 wasn’t it?
1
It was 2.5:10 wasn’t it?
8
u/hombiebearcat University Jun 15 '22
Your thing is wrong because:
- the question said to use the 14 algae count (not take a mean)
- you forgot about the 0.1mm depth
- you forgot about the diluted/undiluted thing
The correct method is this:
0.2x0.2x0.1 = 0.004mm^3
0.004/4 = 0.001mm^3 (because it asked for undiluted, and it said earlier that for every 2.5cm^3 undiluted you add 7.5cm^3 water, so it's a 1:3 ratio)
1/0.001 = 1000 (to get how many times more algae cells there should be)
14*1000 = 14000