S2S - PERT formula

Before I begin...
S2S is Shortcut to Success (for memorizing imp stuff)
imp is Important
CTC is Cut the Crap (for those who're interested in saving their time)

Basics -
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PMO (can be remembered as project mgmt office) in PERT (3-point analysis) stands for Pessimistic, Most likely and Optimistic values respectively.
P>M>O alws (remember full form of PMO?)

To give M more weightage it's multiplied by 4 and then the sum of P,4M and O is divided by 6 (=1 for P + 4 for M + 1 for O)

So we have

(P+4M+O) / (1+4+1=6)

So you learned the formula.
But,
to calculate in competitive exams u ll face difficulty if numbers P,M,O are large (calculation of multiply by 4 and divide by 6 could go wrong or take time) or very easy (silly mistake may happen)

A fact - This multiplication of 4 makes the final answer closer to M. In case you don't have time to calculate can tick any option near M.

If there are many options near M, at least check the final answer would be M, less than M or more than M.
So find out d(m,p) and d(m,o) by subtracting smaller (of P,M,O) from bigger consecutive one..
So

d(m,p) = P - M (cuz M is smaller)
d(m,o) = M - O (cuz M is bigger)


Did u notice we are positive minded people and that's why subtracting smaller from bigger..
Also we gave M more weightage while naming the differentiation d(m,p) and d(m,o) no matter M was smaller or bigger.

Now probably u guessed why d's are used? It did not just made the two numbers u were dealing with (P & O) smaller but also more relevant...bringing u closer to the answer (from closer to the question)..here on we have to concentrate on d(m,p), M and d(m,o) only...

The differentiation farther (again bigger) from M pulls the PERT answer towards it (P or O)

if d(m,p) > d (m,o) then answer lies between M and P
if d(m,p) < d (m,o) then answer lies between M and O
If d(m,p)=d(m,o) M is the answer.   --Imagine ur calculating the ans from real formula for 1 minute doing a multiplication by a 4 and division by a 6; while answer lied in question itself and it was "M"




CTC
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You still wanna calculate the real number in less time?

I would still suggest to calculate d's cuz if the answer is M, that's shortest calculation to do.

Here's the new formula -
M + [d(m,p) - d(m,o) / 6]
Subtract O's difference from P cuz P>O and we are positive minded ppl.

If you are not convinced or are skeptic about d's then this one is for you

M + [ (P+O-2M) / 6 ]
Remember we have reduced multiplication by 4 to only 2... so this is still a S2S :-)


e.g.:
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It will be good if you apply it in ur way in ur question.