Hello,
Well we can use this technique for couple of problems so its worth learning and understanding .
Say, Distance is constant, then Speed is inversely proportional to time
or we say
\(\frac{Sa}{Sb}\)= \(\frac{Tb}{Ta}\)
or
Speed Time Distance40 m/hr 3hr 12060m/hr 2hr 120So i increased my speed by 50 % or by \(\frac{1}{2}\) , so time will reduce by 33% or by \(\frac{1}{3}\)
So generally increase of \(\frac{1}{x}\) leads to decrease of \(\frac{1}{x+1}\)
Comming back to our question . The price in both the cases is Constant or unchanged. So it must be of the above form.
Let initially the weight be w1 and price initially per gram is x1 and total price is p . Now after reducing the weight be w2 , price per gram is x2 and total price is p
we have x1*w1=p
now if w1 is decreased by 20 % that is by \(\frac{1}{5}\) ( note decrease is always on the form of \(\frac{1}{x+1}\) so \(\frac{1}{5}\)=\(\frac{1}{4+1}\) that means the corresponding price per ounce must rise by \(\frac{1}{x}\) which is\(\frac{1}{4}\) = 25% to keep the price p constant .
Hope i was able to put forward the method of indirect variation correctly.
Probus.
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Probus
~You Just Can't beat the person who never gives up~ Babe Ruth