A Level Biology exam question (maths type)

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fireturtle
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Hi, was wondering if anyone knew how to work out this question, don't know how to approach it.

In humans, after the gametes join at fertilisation, every cell of the developing embryo undergoes mitotic divisions before the embryo attaches to the uterus lining.
The first cell division takes 24 hours.
The subsequent divisions each take 8 hours.
After 3 days, the embryo has a total volume of 4.2 x 10(-3)mm(3).
What is the mean volume of each cell after 3 days? Express your answer in standard form.


Sidenote: numbers in brackets mean that it is a power
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TSR Jessica
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Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.
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username2199397
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Where is this from? It's soo hard
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username2199397
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I assume you need to calculate the number of cells present within 3 days. Then divide the volume by the number of cells. So within the first day you get 2 cells. Then divide 48 by 8 which is 6 more divisions. So that's 128 cells in 3 days. Now 4.2x10^-3 ÷ 128 = 3.28125×10^-5.

The question wasn't that bad actually. Just think logically.
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shum1614
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(Original post by shohaib712)
I assume you need to calculate the number of cells present within 3 days. Then divide the volume by the number of cells. So within the first day you get 2 cells. Then divide 48 by 8 which is 6 more divisions. So that's 128 cells in 3 days. Now 4.2x10^-3 ÷ 128 = 3.28125×10^-5.

The question wasn't that bad actually. Just think logically.
where did the 48 come from
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Itori
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The way I got it was:The first division is 24h (as stated in the question) which is 1 day. So in 3 days (x24h), you get 72h. Rereading the information given, the first 24 hours of these 72 total are spend on only the first division. so 72-24= 48 hours are divided equally for all the other subsequent divisions. Each subsequent division (as stated) takes 8 hours. So do 48/8 to get 6. This means that you have 7 divisions in total for 3 days. Those 6 divisions you can draw out like 1 dividing into 2, 2 dividing into 4, 4 dividing into 8, 8 dividing into 16, 16 dividing into 32 and finally 32 dividing into 64. You can draw out a tree if it helps you with each branching into two. The logical-mathematical way is just do 2 to the power of 7 to get 128. Mean volume will be total volume (given in question) over the total number of cells so you do 4.2x10(to the power of -3) / 128= 3.3x10(to the power of -5).

.Hope that helps.
Last edited by Itori; 1 year ago
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