Wednesday, September 30, 2009

5 most overlooked points while solving GMAT number based problems (Arithmetic based problems)

The 5 series!!!!

5 most overlooked points while solving GMAT number based problems (Arithmetic based problems)

1.Study the factors of a number. Factors of a numbers are numbers which can divide that number. The factors for 28 are1, 2, 4, 7, 14, 28. Factors are always smaller than a number. The number of factors for a square is always odd.

2.Study the multiples of a number. Multiples of a number are numbers which are obtained by multiplying a given number by a constant. When you want to combine two numbers use LCM. For example : What is the smallest 4 digit number which can be divided by 2,5,6,8 and 9. To solve this sum first: you would have to combine these numbers to arrive at a common number i.e.the LCM of 2,5,6,8 and 9 and then proceed to obtain the smallest 4 digit number.

3.Any number raised to the power of 4 will lead to a number (say k)whose last digit remains the same irrespective of the number of time the number is multiplied with itself.(k x k x k…..n times where n can be any integer)

4.Let a × b = c. The remainder obtained when you divide c by d is equal to the product of the remainders obtained when you divide a by d and b by d. Instead of finding the remainder of 625 when divided by 7 it would make sense find the remainder of 25 when divided by 7 and multiplying the remainder twice to get the overall remainder( 625 =25 x 25)

5.While solving number based data sufficiency problems substitution of all possible numbers (positive integers, negative integers, positive fractions, negative fractions, zero) is necessary before arriving at an answer.

For example: Is (a/b) > (c/d)
1. a > c
2. b >d

Each statement individually will not yield an answer. When the statements are taken together substitute positive numbers, negative numbers to check the consistency of the answer. Also substitute numbers which are near each other as per the number line (a=2,c=1) and numbers which are far away (a =1000, c=1)

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