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## Mathcad Prime 3 solver block

I'm slightly confused, can any one see why this will not solve.  I have 4 equations and 4 unknowns.

any help would be greatly appreciated.

I have tried putting all the static values in the guess values Tags (2)
6 REPLIES 6
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Hi David,

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## Re: Mathcad Prime 3 solver block

File attached now

I looked for that option when I was posting before

Thank you

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## Re: Mathcad Prime 3 solver block

It perhaps can't find an equality because there isn't one.  I replaced find with minerr and your equations appear to be quite sensitive to initial conditions.

Stuart Highlighted

## Re: Mathcad Prime 3 solver block

Strange that it cant find an answer as the truck is driving down the road.  the answer above does not satisfy the first equation

R1+R2+R3+R4=A1+A2+A3+A4+KP

In the real world I would expect to see the majority of the load imposed from Kp to be in R3 and R4

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## Re: Mathcad Prime 3 solver block

 David Callaghan wrote: Strange that it cant find an answer as the truck is driving down the road.

All I can suggest you do is get that truck off the road immediately.  Operated a vehicle not in accordance with the laws of physics is a contravention of the Road Traffic Act and liable for 3 penalty points and a fine not exceeding £250! the answer above does not satisfy the first equation R1+R2+R3+R4=A1+A2+A3+A4+KP In the real world I would expect to see the majority of the load imposed from Kp to be in R3 and R4

I did a bit of rearranging, putting the inequalities into functions and checked the case where KP = 0 kg ... I'm guessing this should make R = A?  If so, then the expressions for r1 and r4 may need a closer look. Stuart

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## Re: Mathcad Prime 3 solver block

 StuartBruff wrote: David Callaghan wrote: Strange that it cant find an answer as the truck is driving down the road.  All I can suggest you do is get that truck off the road immediately.  Operated a vehicle not in accordance with the laws of physics is a contravention of the Road Traffic Act and liable for 3 penalty points and a fine not exceeding £250! the answer above does not satisfy the first equation R1+R2+R3+R4=A1+A2+A3+A4+KP In the real world I would expect to see the majority of the load imposed from Kp to be in R3 and R4 I did a bit of rearranging, putting the inequalities into functions and checked the case where KP = 0 kg ... I'm guessing this should make R = A?  If so, then the expressions for r1 and r4 may need a closer look. Stuart

Found the problem.  In the expression for balancing about R1, the A terms are parenthetically grouped, but they are subtracted not added inside the parentheses.  In the expression for R4, L2 appears twice in the A1 term, not L3.  Correcting the expressions allows find to do what it says on the label. Stuart