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Best technique to solve problems like these.Anyone??

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Best technique to solve problems like these.Anyone??

by dddanny2006 » Thu Nov 07, 2013 9:19 am
1.If x is an integer,is x odd?

(1)x+4 is an odd integer
(2)x/3 is NOT an even integer

2.If is a positive integer ,is sqrt(d) an integer?

1.Sqrt(9d) is an integer
2.Sqrt(10d) is NOT an integer

and other similar problems..

Whats the best technique to solve these?In problem 1,we can equate x+4=say, 3 and we can then find sufficiency?Or another method to do the same is to substitute different values for x and then check for sufficiency.Whats the best technique to solve problems like these.I know the answers to these problems.I just want to know a fool-proof technique that will leave no stone unturned. Because I have made mistakes when I usually equate the statements to something.If there's an effective technique,or is substitution(we insert values for x)is a better method to tackle problems like these.

Thanks


Dan
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Source: — Data Sufficiency |

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by [email protected] » Thu Nov 07, 2013 12:25 pm
Hi dddanny2006,

Both of these questions are based on Number Properties, which means that they can ALSO be solved by TESTing Values. You can ultimately decide how you want to do the work, BUT you should plan on writing everything down so that you avoid any silly mistakes that might be costing you points.

Q1. X is an integer. Is X odd? This is a Yes/No Question

Fact 1: X+4 = odd

The Number Property is X + even = odd
X MUST be ODD because Odd + Even = Odd
The answer to the question is ALWAYS YES
Fact 1 is SUFFICIENT

You COULD TEST Values.

X can = 1
X can't = 2 because 2+4 isn't odd
X can = 3
X can't = 4 because 4 + 4 isn't odd
etc.
The only values that "fit" the given information are odd, so X MUST be odd.

Since you already know the answers to the questions, then I'm going to leave the rest of the word for you to finish. Remember to stay flexible; you can use Number Property Rules, TEST Values or BOTH as need be. A good way to think about DS questions is that you NEED proof of what the correct answer is, so gather enough proof before you pick your answer.

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Rich
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by ceilidh.erickson » Fri Nov 08, 2013 1:53 pm
Generally speaking, it's more time-efficient on many number properties questions to understand the CONCEPTS, and to think conceptually rather than testing values. However, come people feel more confident testing values, so it's a matter of personal preference.

Practice each question both ways, and decide for yourself what works better for you!
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
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