For good or bad, competition is here to stay in Indian Higher Education. The admission cut offs in colleges are seeing new highs every year. And the examination patterns of both Board exams as well as entrance tests are changing constantly to take into account the increasing gap between number of seats in premier colleges and the number of applicants vying for them.
A very big change in marking system when a student shifts from board exams to entrance tests is there is no fixed concept of “good marks”. While in school exams there are fixed parameters like 80% or A grades which can be treated as good, in entrance exam the selection process is based on Ranks and percentiles and not really percentage scores. Thus the only principle that works is doing as much as you can. However most of the entrance exam has negative marking for wrong answers and thus accuracy also plays a vital role in the selection process.
Quantitative Aptitude being almost an integral part of almost all major entrance exams now, importance of calculating fast and correct has increased hugely. However with no emphasis on that in the board exams, most of the students try to ignore this part and concentrate more on only accuracy albeit using long traditional text book methods. However the moment they reach the entrance exam stage they find themselves in deep trouble. In most of the entrance exams like that of BBA/BBE in prestigious universities like Delhi University or Symbiosis, students have to attempt around 30-40 questions of Maths in approximately 45 minutes and that is not an easy job.
Unlike the popular perception that fast calculations require lot of hard work and practice, using some basic concepts of Maths, we can actually make calculations faster with just a week’s practice or so.
For example if we need to find the square of a number let’s say 75, we can use simple observations from maths and do it in a flash.
For those numbers where the unit’s digit is 5, the square of those numbers always end with 25. Thus the last two digits of 752 will be 25. For finding the first two digits we just have to multiply 7 (the digits in the ten’s place) with its consecutive number i.e. in this case 8. So the first two digits will be (7×8) = 56
Thus my total result comes out to be 5625.
This property holds true for any number with unit’s digit 5. Thus
352 = (3×4) 25 = 1225
952 = (9×10) 25 = 9025
1052 = (10×11)25 = 11025
Easy isn’t it? And there are more such interesting and easy methods which can save calculation time by more than 50% from your regular method.
In this series we will give some very easily adoptable methods through which you can make your calculations faster without compromising on accuracy. These methods were developed by famous mathematicians over many many years and are very useful not only for exams but for your daily life as well.
Next week we will teach you how do squaring and multiplication of various numbers without using any pen and paper. Watch out this space for more!
Authored by Dhrubajyoti Banik.
Published in Hindustan Times, New Delhi, August 01, 2012.
(The author is chief knowledge officer of HT, Studymate)