Sunday, January 26, 2014

Averages and Mixtures problems | Formulae Shortcuts questions

Mixture and Alligation Shortcut Methods

 
Formulae:
1.       Average = sum of quantities/number of quantities
2.       Sum = avg * no. of quantities
3.       If the numbers are in A.P. (Arithmetic Progression), then the avg of numbers is given by
Avg = sum/n =[ (n/2)(a+l)]/n
                = (a+l)/2
Where  n – no. of quantities
                a – first term or value
                l – last term or value
4.       Weighted Average:
Section1:
                No. of quantities: m
                Avg of section1: p
Section2:
                No. of quantities: n
                Avg of section1: q
Avg of section1 and section2 = (m*p + n*q)/(m +n)

Points to remember/Shortcuts
1.       Average lies between minimum and maximum values.
a.       Avg > minimum value
b.      Avg < maximum value
2.       If every quantity is increased/decreased by ‘k’ value, then the avg also get increased/decreased by the same ‘k’ value.

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