AQA A-level Biology question

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 × 10–3 mm3
.
What is the mean volume of each cell after 3 days? Express your answer in
standard form.
Show your working.

Answer: 3.3 x 10–5 OR 3.28 x 10–5 OR 3.281 x 10–5
;;
1 mark for
Evidence of 128 (cells)
Correct numerical calculation but not in standard
form gains 1 mark (0.00003281 OR 0.0000328 OR
0.000033);
Im not sure how they have calculated the answer to this question

Reply 1

banana_joe

Original post by kit2247

right so the 1st division is 24hrs which is a day. so in 3 days u get 72hrs. 24hrs out of the 72 are solely for the first division so 72-24=48hrs these 48 hrs are for the subsequent divisions which takes 8hrs so 48/8hrs gives u 6 more divisions so a total of 7 divisions. u can draw the diagrams where 1 turns to 2 the 2 gives 4 and so on or mathematically u just make it 2 to the power of 7 which gives 128 cells in total. then u get mean by taking the volume of 4.4*10^-3 divide by 128 gives the 3.28*10^-5