Quantitative Ability

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Change of base (15 mins)

Start with the simplest problem: If A is 20% more than B, by what percent is B less than A? Do the
same problem if A was 37.5% more than B. Explain why it is important to work with fraction equivalents
to save time & calculations.


Successive Percent changes (10 mins)
Take a simple case of two successive increases say 10% and 20% and then explain why the total
increase is 32%. State that the net increase of an (a%) and a (b%) change is a (a + b + ab/100%)
change. Do mention that the formula works fine with any changes viz. increase or decreases. Ask
student to find the net percentage change of a x% increase and a x% decrease and also for a 10%
increase and a 9.0909% decrease. Probably the last example can be more easily solved with multiplying
factors. Thus one can use Multiplying factors or a + b + ab/100 interchangeably.



Interest on Interest (10 mins)
With the above table still present on the board, explain point number d of above in more details.
Explain that in any year the CI earned is higher because whatever was earned in the previous year
would surely be earned and additionally the interest earned in previous year will also be added to the
principal and start earning interest. Make sure this concept of Interest on Interest is understood by
everyone.