Apti tricks

Mathematical Aptitude - Tips & Tricks www.aptiDude.com
www.aptiDude.com
Copyright @ 2014, content compiled by aptiDude.com team and mathematical experts

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
For more such tips & tricks, get access to the complete
book of Aptitude Tips, Tricks & Formulae for All
Competitive Exams, here:
http://www.wiziq.com/course/56253-aptitude-tips-tricks-
formulae-for-all-competitive-exams

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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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