Math help please

[Gamom3]

Ds is working on Direct and Inverse Variations

He pretty much understands what to do, but he came upon a problem that has confused him/us.

 

He is using Chalkdust pre-algebra 7.4 Q 37 which is a Physics question

 

Here's the Q:

 

For a constant temperature, the pressure(P) of a gas varies inversely as the volume(V). If the pressure is 25 lb/in^2 when the volume is 400ft^3, find the pressure when the volume is 150ft^3. Round to the nearest hundredth.

 

He thought that the first mentioned would go first..which is what he has been doing the whole chapter.

So he was writing P=k/V

 

but the answer key did V=k/P

Can someone tell me why?

 

Thanks

[kiana]

I'm not completely sure why the answer key started it that way, but the two equations are equivalent and his method is not wrong.

[Gamom3]

Thats what was throwing us off.

 

 

Thanks!!

[fractalgal]

Ds is working on Direct and Inverse Variations

He pretty much understands what to do, but he came upon a problem that has confused him/us.

 

He is using Chalkdust pre-algebra 7.4 Q 37 which is a Physics question

 

Here's the Q:

 

For a constant temperature, the pressure(P) of a gas varies inversely as the volume(V). If the pressure is 25 lb/in^2 when the volume is 400ft^3, find the pressure when the volume is 150ft^3. Round to the nearest hundredth.

 

He thought that the first mentioned would go first..which is what he has been doing the whole chapter.

So he was writing P=k/V

 

but the answer key did V=k/P

Can someone tell me why?

 

Thanks

 

When written V=k/P, it is implied that the volume (V) is the dependent variable and the pressure (P) is the independent variable if this is thought of in terms of a function.