2. Flash card set 1
Topic covered- arithmetic
Flash cards set 2 to set 20 will be uploaded at
http://letsgmat.blogspot.com

3. Science of thinking (ScoT bytes) 1
on fibonacci series
For any four consecutive numbers which are in a Fibonacci series i.e. A,B,C
and D
C2
- B2
=A x D
on a series of numbers
If n is odd n(n2
-1) is divisible by 24
If n is odd 2n
+1 is divisible by 3 and if n is even 2n
-1 is divisible by 3
If n is odd 22n
+1 is divisible by 5 and if n is even 22n
-1 is divisible by 5
xn
+ yn
=(x+y)(xn-1
-xn-2
y+……..yn-1
)
xn
+ yn
is divisible by x+y when n is odd
xn
- yn
is divisible by x+y and x-y when n is even
xn
- yn
is divisible by x-y when n is odd
xn
- yn
is always divisible by x-y

4. Science of thinking (ScoT bytes) 2
on squares
A square cannot end with 2,3,7 or 8 and it cannot end with an odd numbe
zeros
Every square number is a multiple of 3 or exceeds a multiple of 3 by 1
Every square number is a multiple of 4 or exceeds a multiple of 4 by 1
on HCF and LCM
Let A and B be two numbers, then
Product of A and B = HCF (A, B) × LCM (A, B)
on odd and even numbers
(Even number)4x
will always end in the digit: ‘6’
(Odd number)4x
will always end in the digit: ‘1’

5. Science of thinking (ScoT bytes) 3
on remainders
The remainder obtained when you divide c by d is equal to the product of
remainders obtained when you divide a by d and b by d.
on percentages
When the word ‘lesser than’ or the word ‘more than’ is used in the
question,
the percentage increase formula must be used. The number after the word
‘than’ is usually the initial value.
If a is increased/decreased by b%, then the new value calculated after the
increase is, new value = a ± b% of a ±
Adding two percentage a% + b% doesn’t give (a + b) %, it gives
a% ± b% =
b
× a
100
ab
a ± b ± %
100
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6. Science of thinking (ScoT bytes) 4
on simple and compound interest
The SI and CI remain same at the end of one year. The amount as well as
the compound interest increase by r% every year. If principal = 100 rate =
10% P.A then
on ratios
If a:b = 3:4 then a and b are not equal to 3 and 4 respectively. a = 3x and b
= 4x where x is any constant.
If a ratio a/b is given such that or a>b and there is an integer x such
that x is positive then and
If a ratio a/b is given such that or a < b and there is an integer x such
that x is positive then and
Year 0 Year 1 Year 2 Year 3
Amount = 100 110 (100 + 10%) 121 (110 + 10%) 133.1 (121 + 10%)
CI (interest) = 0 10 11 (10 + 10%) 12.1 (11 + 10%)
SI (interest) = 0 10 10 10
a
1
b
>
a+x a
b+x b
<
a - x a
b - x b
>
a
1
b
<
a+x a
b+x b
> a - x a
b - x b
<

7. Science of thinking (ScoT bytes) 5
on alligations
When different quantities of same or different ingredients of different valu
are mixed together to produce a mixture of a mean value, use alligation.
Rule of alligation
CP of unit quantity of cheaper(a) CP of unit quantity dearer(b)
Mean price (x)
(b-x) (x-a)
Quantity of cheaper CP of dearer - Mean price
Quantity of dearer Mean price - CP of cheaper
=
Cheap quantity b-x
dearer quantity x-a
=

8. Science of thinking (ScoT bytes) 6
on mixtures
In a mixture containing two inseparable liquids, use this formula to compute
the percentage of each liquid after replacing the liquid with the larger
percentage with the liquid with smaller percentage n times.
Nos. of times
initial amount of liquid – constant amount taken out
xinitialamount of liquid
initial amount of liquid
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