Quant Theory

1) Sum of interior angles of a polygon with n sides = (n-2)*180

2) Degree measure of one angle in a regular polygon with n sides= {(n-2)*180 }/n

3) When multiplying or dividing both sides of an inequality by anegative number,

the inequality sign reverses.

–x < y => -(-x) > y => x > -y

4) Fraction > (fraction)2 for all positive fractions

5) Fraction > v(fraction ) for all positive fractions

6) If n is a positive integer, (n6)/2 = v(n12 / 4)

7) If z1, z2, z3 … zn are consecutive positive integers and their average is an odd integer => n is odd => sum of series is odd

8) In a triangle with sides of measure a, b and cSHAPE \* MERGEFORMAT , a-b

9) Before confirming try and back solve and make sure that u have answered what has been asked.

10) When the question mentions prime number, remember to think of 2 too.

11) In a triangle, if the sum of two angles = third angle, then it is a right angled triangle.

12) Do not transport information from another statement unless considering both collectively.

13) A-b = odd => a + b = odd

14) If a DS question simply asks whether a, b, c and d are consecutive integers;

use your brain. It has just asked u to answer if they are consecutive,

not if they are consecutive in order.

15) Measure of an angle of a cyclic polygon = 180 – 360/n ,

where n is the number of sides of the polygon.

16) Sometimes, mistakes might also be committed by simply misreading the statement. Eg

Both Tim and Harry received an acre of land more than Neel => t = n + 1, h = n + 1

Tim and Harry received an acre more than Neel => t + h = n+1

17) Two circles will touch each or intersect each other if the distance between their centers d is such that

R – r ? d ? R + r, where R and r are the radii of the two circles

18) Remainder of less than two means not just one; it also means remainder of zero.

19) Do not make unwarranted assumptions. 12 midnight to 12 noon does not mention what days, and hence you cannot find out the time period.

20) Standard deviation of a set is always negative and equals zero only if all elements of the set are equal.

21) If the difference between the largest and the smallest divisor of a number is X, the number is X + 1

22) Always remember the special watch out cases in DS questions. If the question mentions mean of a set, the mean can be ZERO also.

23) If area of a rectangle is known, diagonal is known, perimeter can be found

a^2 + b^2 = diagonal^2

a^2 + b^2 + 2ab = diagonal^2+ 2ab

(a + b)2 = diagonal^2+ 2*area

24) v(y^2) = |y| => y if y is positive, -y if y is negative

25) angle = mod [(60H - 11M) /2 ]

H = value of hour hand

M = value of minute hand

eg, if time is 2:30, then H =2 and M =30

26) Every number raised to power 5 has the number itself as unit digit

27) If a + b + c = Z, than the largest of a, b, and c cannot be greater than the mean of the other two.

28) The rule that one side of a triangle cannot be > sum of other two, only applies to sides, not angles

29) FINALLY, MAKE SURE OF WHAT THE QUESTION SAYS – INTEGER MEANS INTEGRAL LENGTH. And, DIVIDING A WIRE INTO PIECES, DOES NOT NECESSARILY IMPLY THAT THEY WILL BE INTEGRAL LENGTHS. Similarly, that a boat covers a distance upstream in 3 hours, states only the time, even if it has been mentioned that it covers a a distance 12 km downstream in 2 hours.

30) x^2 = 9*y^2 does not necessarily imply that x^2 > y^2. (Hint : consider x=y=0)

31) When we say multiples between 16 and 260, and inclusive/exclusive is not mentioned, take 16 and 260 to be exclusive.

32) The statement implies :

The hourly wage for each employee ranges from $5 an hour to $20 an hour.

minimum average = (20 + 5 + 5 + 5 + 5)/5

maximum average = (5 + 20 + 20 + 20 + 20)/5