Tricks and tips of Calculations in GRE Quantitative Reasoning

Tricks and tips of Calculations in GRE Quantitative Reasoning

Concision in thoughts aids a lot to drive the decision of calculations utilizing the best use of time in GRE test. Concision of calculations creates a time saving criterion. In a typical examination, each quantitative section consists of 20 questions to be completed in 35 minutes. So anyone’ll have between 1.5 and 2 minutes to answer each question. One’ll have to limit the time spend on each math question. Though GRE on-screen calculator allows simple calculations, one should try to avoid using it every now and then. Indeed, an examinee should only need it for a couple of questions. So, each of us should practice functioning simple & possible conversions and mathematics through the resonance of our brain to with the strategical style of concise calculation.

Rules of divisibility

One should save some rules of divisibility so that he/she can save the time without wasting it in searching each choice answers using all details in questions and calculator. For example, if one is asked that which of the following numbers are divisible by 4 : 3456, 3546. Yes, we can check it with the on-screen calculator but if we apply our adapted & saved strategies we do not need to use the calculator or do it in the rough paper then we can save a vital time ranges.

1. Any number is divisible 2 when the last digit of the number is divisible by 2 [or when the last digit is 0, 2, 4, 6 or 8] e.g: 95352 is divisible by 2.
2. A number is divisible by 4 if the number formed by its last two digits is divided by 4, e.g: 3456, 3546 gives 56 and 46 as numbers from their last two digits where 56 is divided by 4 but 46 is not. So, only 3456 is divisible by 4.
3. A number is divided by 8 if the number formed by its last three digits is divided by 8, e.g: 7654128 is divisible by 8 because 128/8 = 16.
4. A number is divisible by 3 if the sum of all its digits can be divided by 3, e.g: 170682 is divisible by 3 and here the sum of the digits are (1+7+0+8+6+2) = 24, which is divisible by 3.
5. A number is divisible by 9 if the sum of all its digits can be divided by 9, e.g: 58421502 is divisible by 9 and here the sum of the digits are (5+8+4+2+1+5+0+2) =27, which is divisible by 9.
6. Any number is divisible by 6 (2x3) if the number is divided both by 2 and 3 i.e the number will follow rule 1 and 2 mentioned above.
7. Any number is divisible by 5 if the last digit of the number is 0 or 5, e.g: 390, 935 etc are divisible by 5.
8. If the last digit of any number is 0 then the number is to be divided by 10.
9. A number is divisible by 11 if the difference between sum of the digit in the positions and sum of the digit in the even positions, e.g: In 62678, the difference = (6+6+8)-(2+7) = 11 which is divided by 11.

 

Estimation of approximation

In order to compare or find out answers to few questions of quant section one does not always need to do the exact calculation precisely which may even consume the vital time. For example, if the question is set to find the product of 51.3773 and 8998 we can approximate them to 50 and 9000 respectively which helps us to do the math with a fast mental potential giving us a result of approximation. Again if we need to compare 12(4x3) & 4π(4x3.1516), as π = 3.1416>3, so we can infer without doing the calculation that 4π>12. This approximation gives a very nearer value and aids us to match it and select the correct answers even without using a calculator on the screen. Estimation of approximation thus saves the time of the test.

Strategy to divide number ended with 5

If a number N is ended with 5 the quotient or result can be obtained faster in doing (2N/10) than (N/5) directly e.g: If we try 2335/5 and 4670/10 simultaneously the later will give the faster answer as 467 i.e 2335/5 = 467.

Strategy to square number ended in 5

If the number given is N5 then the square of N5 is M25 where M=[Nx(N+1)].  If the number is 475 then N=47 and N+1 = 48 , M= Nx(N+1) = (47x48) = 2256. So , the square is M25 or 225625.

The strategy to square a number ending in 5 is to remove the 5 and leave the remaining digits for example if we have 475 then leaving 5 we get 47. If we add 1 and get 48 to multiply it with 47 which give (47x48) or (47x2x24) or (94x4x6) or (376x6) or 2256. We know the square of 5 is always 25. Now, if we put the 2256 before the square of leaving 5 earlier got as 225625 which is the square of 475. It is recommended to follow the way of multiplication doing above for saving time because simplicity is the keynote of smart time management to score with excel.

A general strategy to square a number

If one needs to find the square of a number which can be expressed as (n+1) or (n-1) where we know the square of n then the square of the number is to be [n²+n+(n+1)] or [n²-n-(n-1)] respectively, e.g: If we are given 81 & 84 to find their square then ,

81= 80+1 ,  we know 80² = 6400 , so 81² =80² + 80 + (80+1) = 6561 

84 = 85-1 , we can see 85 is ended in 5 so, we know, 85² = M25= 7225, where M=8x(8+1).

Actions to take in comparision

If both columns of quantitative comparison contains number or numerical identities then there must be some definite relationship (=,>,<) etc. between the 2 quantities which states that the option (D) inscribed as ‘The relationship cannot be determined from the information given’ cannot be the correct answer to choose. We can take action by operating same positive number with the two comparable quantity. The operations can be addition, subtraction, multiplication or division to simplify the quantity to save time.

The math section of GRE deals with the logical lucidity with the level of understanding where simplicity is the fuel to start up and go onward with the strategic art of precision and concision.