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# Re-arranging Equation watch

1. Hi I have this equation, c= (10000qp/q) + cf

Cf is the concentration of co2 in the incoming air which is 3 in a room

qp is the average production of co2 by a person in a room which is 4.7 x 10 ^-6 m^3 s^-1

C is the concentration of co2 in the room which must not exceed 10

q is the room volume at 340 ^m3 for 14 people

The question is if 21 people are in the room, to what value must q be increased to.

thank you
2. Which of the letters represents the No of people?
3. Hi,

sorry, the full formula is,

it is actually c = (10000qpN3600)/q + cf

3600 is the time in seconds at which a room of 340^m3 recives a change of air.

N = the number of people

thanx
4. (Original post by Samh)
Hi,

sorry, the full formula is,

it is actually c = (10000qpN3600)/q + cf

3600 is the time in seconds at which a room of 340^m3 recives a change of air.

N = the number of people

thanx
I worked the answer out as 507.6 m^3 for new value of q I dont know if it is right or not.
5. You know you really should do your own homework

OK replacing the algebra for known values.

c=((10000*3600*4.7*10^-6*N)/340)+3
= ((169.2*N)/340)+3

for 14 people c will equal 9.96

for 21 people to get a value of C=10 and assuming that cf stays about the same

10=(169.2*21)/q+3
10-3=3553.2/q
7q=3553.2
q=507.6m^3

This would best be rounded up to 510m^3 to keep C below 10.

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