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Re: gmat prep question

by gabriel » Fri Apr 13, 2007 4:54 am
yvonne12 wrote:Is the hundredths digit of the decimal d greater than 5?
I. the tenth digit of 10d is 7
II. the thousandths digit of d/10 is 7


why is it each?
consider the number d to be equal to a.bcde ... b is the tenth digit , c is the hundredths digit, d is the thousandths digit and so on ..

so what the q asks is if the hundredths digit (that is c) is > 5

the first statement says that in 10d the tenth digit is 7 .. so 10*d = 10*a.bcde = ab.cde .. so in this number the tenth digit is c which is given to be 7 .. which is > 5 .. so is sufficient ...

the second statement says that the thousands digit is of d/10 is 7 ... now d/10 = a.bcde/10 = 0.abcde .. in this number the thousands digit is c .. which is given to be 7 .. which is again > 5 ... so 2nd statement is sufficient ..

.. so the answer is D ...
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Re: gmat prep question

by guynoor » Fri Apr 13, 2007 6:28 am
yvonne12 wrote:Is the hundredths digit of the decimal d greater than 5?
I. the tenth digit of 10d is 7
II. the thousandths digit of d/10 is 7


why is it each?
1) SAYS 10 * ._ _ = _ . 7
t h t

NOW THE TENTH DIGIT OF THE RESULT ABOVE (I.E 7) IS ALSO THE HUNDREDTH DIGIT OF 10 * . _ _ ( OR 10*D ) HENCE 7 > 5 SO SUFFICIENT.

2) SAYS ._ _ / 10 = . _ _ 7
t h

NOW WE CAN SEE THAT THE THOUSANTH DIGIT OF D / 10 IS 7, WHICH IS ALSO THE HUNDRETH DIGIT OF D ( YOU CAN MULTIPLY D BY 10 AND SEE THIS ) SO 7 > 5 HENCE SUFFICIENT

PS - I AM NOT ABLE TO GET THE FORMATTING RIGHT ON T,H ETC BUT YOU GET THE POINT.
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makes sense

by yvonne12 » Fri Apr 13, 2007 7:07 pm
Gabriel the way you put it, makes alot of sense. I didnt think of it that way. Thanks this should help
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Re: gmat prep question

by mehravikas » Sat Oct 25, 2008 3:38 pm
Thanks for this explanation. I always had problems with these decimal questions. Your explanation is very well described.

gabriel wrote:
yvonne12 wrote:Is the hundredths digit of the decimal d greater than 5?
I. the tenth digit of 10d is 7
II. the thousandths digit of d/10 is 7


why is it each?
consider the number d to be equal to a.bcde ... b is the tenth digit , c is the hundredths digit, d is the thousandths digit and so on ..

so what the q asks is if the hundredths digit (that is c) is > 5

the first statement says that in 10d the tenth digit is 7 .. so 10*d = 10*a.bcde = ab.cde .. so in this number the tenth digit is c which is given to be 7 .. which is > 5 .. so is sufficient ...

the second statement says that the thousands digit is of d/10 is 7 ... now d/10 = a.bcde/10 = 0.abcde .. in this number the thousands digit is c .. which is given to be 7 .. which is again > 5 ... so 2nd statement is sufficient ..

.. so the answer is D ...
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