# Thread: How to Rearrange formula? Solve 2(Pc - d) / Pc for Pc

1. ## How to Rearrange formula? Solve 2(Pc - d) / Pc for Pc

Hello,

Having trouble rearranging formula to solve for Pc. Formula is 2(Pc - d) / Pc.

Any ideas would be appreciated.

2. Originally Posted by SeabeeDavid
Hello,

Having trouble rearranging formula to solve for Pc. Formula is 2(Pc - d) / Pc.

Any ideas would be appreciated.
What are your thoughts?

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3. ## How to rearrange formula

I know the basic rules for rearrangement, but don't quite understand when its not set against and = sign, and I have Pc in the dividend and divisor.

1) 2(Pc - d) / Pc

2) 2Pc - 2d / Pc

3) Pc * (2Pc - 2d) / Pc * Pc

4) Pc(2Pc - 2d)

5) 2Pc Squared - 2dPc

It just doesn't make any sense to me.....

4. Originally Posted by SeabeeDavid
2(Pc - d) / Pc
I'm assuming that Pc is a single symbol (not P times c).

This is not an equation, so there is nothing to solve. This is an expression. We can rewrite expressions (sometimes called simplifying), but I wouldn't necessarily say that the following version is simpler.

2(1 - d/Pc)

Please post the entire exercise statement, including all instructions, word for word.

5. Originally Posted by mmm4444bot
I'm assuming that Pc is a single symbol (not P times c).

This is not an equation, so there is nothing to solve. This is an expression. We can rewrite expressions (sometimes called simplifying), but I wouldn't necessarily say that the following version is simpler.

2(1 - d/Pc)

Please post the entire exercise statement, including all instructions, word for word.
This is a formula for Boiler inspectors to determine allowable circumferential pitch of boiler tubes.
d = 3.03125" (Boiler tube diameter)
Pc = ??? (Circumferential pitch of adjacent openings in ")

Problem: The drum of a bent tube type boiler is drilled for tube holes 3.03125" diameter spaced longitudinally in groups of two tubes pitched 4.875 with 6" spaced between groups. Circumferentially tube holes are symetrical. What is the circumferential pitch of the tubes. Solve for Pc

6. Originally Posted by SeabeeDavid
This is a formula …
I'm sorry, but it is not a formula.

All formulas contain an equals sign.

7. I googled some keywords, and I found a number of sites from which you may download ASME Sec. 1 (2010).

The longitudinal pitch between the staybolts, or between the nearest row of staybolts and the row of rivets at the joints between the furnace sheet and the tube sheet or the furnace sheet and mud ring, shall not exceed that given by the following formula: 56320t2L=2PR where L = longitudinal pitch of staybolts, P = maximum allowable working pressure (pounds per square inch), t = thickness of furnace sheet (inches), R = outside radius of furnace (inches). When values by this formula are less than the circumferential pitch, the longitudinal pitch may be as large as the allowable circumferential pitch. The stress in the staybolts shall not exceed 7500 psi. and shall be determined as specified in PFT-23.4.23.4 In furnaces over 38 in. in outside diameter and combustion chambers not covered by special rules in this Section which have curved sheets subject to pressure on the convex side, neither the circumferential nor longitudinal pitches of the staybolts shall exceed 1.05 times that given by the rules in PG-46.
That is an example of a formula.

8. Originally Posted by mmm4444bot
I'm sorry, but it is not a formula.

All formulas contain an equals sign.

9. Originally Posted by mmm4444bot
I googled some keywords, and I found a number of sites from which you may download ASME Sec. 1 (2010).

That is an example of a formula.
This formula is directly out of the ASME Section 1 (2017) book. Is it possible to solve for Pc?

10. Originally Posted by SeabeeDavid
A = 2(Pc-d)/Pc
This equation can be solved for Pc.

I'll get you started.

1) Multiply each side by Pc

2) Use the Distributive Property, to multiply out 2(Pc - d)

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