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Mathematical Aptitude - Tips & Tricks www.aptiDude.com

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Copyright @ 2014, content compiled by aptiDude.com team and mathematical experts

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www.aptiDude.com

Copyright @ 2013, content compiled by aptiDude.com officials and mathematical experts

PROBABILITY TRICK

Apti Trick - THE BIRTHDAY PROBLEM

Out of n persons, the possibility that birthdays of two persons don’t coincide is given by

P (Not Same Birthday) = 365Pn / 365n

Similarly, the possibility that at least two of them will have the same birthdays is given by….

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NUMBER SYSTEM

How many times a digit ‘n’ appears in a certain range (except 0)?

From 1 – 9, the digit ‘n’ is used 1 time

From 1 – 99, the digit ‘n’ is used 20 times.

From 1 – 999, the digit ‘n’ is used 300 times

From 1 – 9999, the digit ‘n’ is used …..


PERECENTAGES

Quick Calculation of Percentages

15 % of 290 ?

Now, 10 % of 290 = 29, 5 % is half of it = 14.5

Hence, 15 % 0f 290 = 29 + 14.5 = 43.5




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PROFIT/LOSS

BUY X & GET Y FREE OFFER

If articles worth Rs X are bought and articles worth Rs. Y are obtained free along with the Rs. X articles, then Discount = Rs. Y

Discount % = (Y / X+Y) * 100


SIMPLE/COMPOUND INTEREST

Difference between Simple Interest & Compound Interest

PROGRESSIONS

1. It is always convenient to take three terms in an A.P. as (a – d), a & (a + d). Four terms in an A.P. could be

taken as a – 3d, a – d, a + d and a + 3d.

2. If nth term of any sequence is Tn = 3n + 2, then (n+1)th term will be …..


Years S.I C.I Difference

After 1 year

PR/100

PR/100

0

After 2 years PR/100

PR

100+ 3P

R

100 2

P R

100 2

After 3 years

PR/100

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Time-Speed-Distance

Application of Relative Speed in Train Problems

Train 1, Length L1, Speed S1

Train 2, Length L2, Speed S2

Sobj be the speed of any moving object

T=Time taken by the train to cross the object

Then,

1. If Train of Length L1 crosses any stationary object of negligible length, then T = L1 / S1 2. If Train of Length L1 crosses any moving object of negligible length, then T = ……


PERMUTATIONS & COMBINATIONS

Number of triangles with one side common to a ‘n’ sided polygon = n * (n – 4)

Number of triangles with two sides common to a ‘n’ sided polygon = n

Number of triangles with no side common to that of a ‘n’ sided polygon = …….


TIME & WORK

If A and B together can do a piece of work in x days, B and C together can do in y days and C and A together can

do in z days, then the same work can be done

By A alone in 2xyz / (xy + yz - zx) days

By B alone in ……. days








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Geometrical Mensurations

PROPERTIES of POLYGONS

For any ‘n’ sided polygon Measure of Each Interior Angle = (n - 2)*1800 / n

Measure of Each Exterior Angle = 3600/n

Number of Diagonals = …..


QUADRATIC EQUATIONS

DESCARTE’s RULE of SIGNS

If the coefficients of all the powers of x of an equation are positive, the equation does not have any positive

root For example, the equation x4 + 4x3 + 5x2 + 9x + 1 = 0 will have no positive root.

If the coefficients of all even powers of x in an equation are of one sign and the coefficients of all the odd

powers of x are of the opposite sign, the equation does not have any negative root. The equation x5 – 2x4 + 9x3 – 5x2 + 7x – 20 = 0 will not have any negative root.







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FINDING 3-Digit Squares

Finding 3 digit squares can be a 2 minute process if you practice the following trick

Suppose you have to find square of 192

Then just round up / down the given number to nearest multiple of 100 as follows

+8 200

192 36800 + 82 = 36800 + 64 = 36864

-8 184

CLOCKS

Speed of Hour and = 3600/ 6 = 60/second

Speed of Minute Hand

= 3600/ (60 x 12) = 0.50/second Relative Speed of Hour and Minute Hands

= 60 – 0.50 = (11/2) 0/second =5.50/second Minute and hour hands meet for 11 times in 12 hours Hands of clock will be 22 times at right angle to each other in 12 hours. Angle between two hands of a clock is given by

|30H – 11/2M|0

.........To be Continued

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Here 36,800 = 200 * 184



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