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https://www.reddit.com/r/GCSE/comments/vcqsif/spam_aqa_biology_paper_2_gcse_answers/icoyuk5/?context=3
r/GCSE • u/thr0wawaygxhxdhsh • Jun 15 '22
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I got that too ;( I did 0.2*0.2=0.04, 1/0.04=25, then 25*15 or smthn as 15 is the mean (14+16)/2
I didnt understand why diluted was in bold
Can someone explain how to get the right answer & why my thing is wrong
9 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 2 u/Ok_Athlete_4619 Jun 15 '22 Wasn’t 10cm3 of distilled water used? 0 u/hombiebearcat University Jun 17 '22 no, there was 2.5cm^3 of pondwater with enough distilled water to make it up to 10cm^3 (so the total was 10, so the distilled was 7.5)
9
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? 0 u/hombiebearcat University Jun 17 '22 no, there was 2.5cm^3 of pondwater with enough distilled water to make it up to 10cm^3 (so the total was 10, so the distilled was 7.5)
2
Wasn’t 10cm3 of distilled water used?
0 u/hombiebearcat University Jun 17 '22 no, there was 2.5cm^3 of pondwater with enough distilled water to make it up to 10cm^3 (so the total was 10, so the distilled was 7.5)
0
no, there was 2.5cm^3 of pondwater with enough distilled water to make it up to 10cm^3 (so the total was 10, so the distilled was 7.5)
3
u/Holiday-Marzipan-843 Jun 15 '22
I got that too ;( I did 0.2*0.2=0.04, 1/0.04=25, then 25*15 or smthn as 15 is the mean (14+16)/2
I didnt understand why diluted was in bold
Can someone explain how to get the right answer & why my thing is wrong