# help me biology question

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#1
The scientists determined the mean diameter of muscle fibres in trained mice using
an optical microscope to examine sections of muscle tissue. The circular area (πr2)
of one field of view was 1.25 mm2 . The diameter of this area was equal to the
diameter of 15 muscle fibres.
Using this information, calculate the mean diameter in μm (micrometres) of muscle
fibres in this section of tissue.
0
1 month ago
#2
would it be this?

1.25=pi x r squared

1250 (micrometres) divided by 3.14 = r squared

square root of 398.08 = 19.95

19.95 x 2 = 39.9

39.9 divided by 15= 2.66 micrometres

so each muscle fibre in this sample had a mean diameter of 2.66 micrometers

Im not sure that its right but i think it is just rearranging the equation.
Hopefully someone can check my answer.
0
1 month ago
#3
(Original post by susiebe)
would it be this?

1.25=pi x r squared

1250 (micrometres) divided by 3.14 = r squared

square root of 398.08 = 19.95

19.95 x 2 = 39.9

39.9 divided by 15= 2.66 micrometres

so each muscle fibre in this sample had a mean diameter of 2.66 micrometers

Im not sure that its right but i think it is just rearranging the equation.
Hopefully someone can check my answer.
Hi there,

Nice of you to be so humble and not bigheaded!
I believe there is an error in your units.

When you convert an area in mm^2 into micrometres^2, you need to use a multiplication factor of 1000^2 i.e. !0^6 NOT 1000.

Therefore, the area of one field in mivcrometres^2 is 1.25 X 10^6

This introduces an error of 1/1000 before square-rooting, SO of around 33 after square rooting.

I would think the answer would be about 70 micrometres i.e. [2.6 X 33]

I shall let OP do the actual calculation!
M.
0
1 month ago
#4
I got 84 micrometres. Here's my working, sorry if it's the wrong way around
1
1 month ago
#5
Mzee Haris,

Firstly, I thought I was the earliest bird to get up before the **** starts crowing, but it seems you have an even better alarm clock than my serum cortisol!

I have not looked at your working but did a quick calculation of the error factor [from Susie's work - as per my previous post, which only suggested an order of magnitude for the ans] SO:

(Sqrt of 1000) X 2.66 = 84.1 um,

Mzee M.
0
1 month ago
#6
I will play along and pretend its because I'm organised and productive and get up early.....

It's definitely not because I didn't just do an all nighter to finish uni work... hahaha. Uni life eh
0
1 month ago
#7
(Original post by HarisMalik98)
I got 84 micrometres. Here's my working, sorry if it's the wrong way around
Thank you!
So useful for me to see your working so clearly set out.
1
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