Decimal

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gmatblood: Master | Next Rank: 500 Posts; Posts: 489; Joined: Tue Jul 05, 2011 11:10 amFollowed by: 5 members; Thanked: 28 times

by gmatblood » Wed Nov 02, 2011 11:59 am

Q1

What is the hundredth digit of the decimal Z?
1. The tenth digit of 100Z is 2
2. The unit digit of 1000Z is 2

Q2

Is the hundredths digit of the decimal d greater than 5?
(1) the tenths digit of 10d is 7.
(2) the thousandths digit of d/10 is 7.

Please point the takeaways as well, thanks

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Source: Beat The GMAT — Data Sufficiency | Wed Nov 02, 2011 11:59 am

gmatblood: Master | Next Rank: 500 Posts; Posts: 489; Joined: Tue Jul 05, 2011 11:10 amFollowed by: 5 members; Thanked: 28 times

by gmatblood » Wed Nov 02, 2011 12:02 pm

Detailed explanation needed, not just IMO!!

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rijul007: Legendary Member; Posts: 588; Joined: Sun Oct 16, 2011 9:42 amFollowed by: 9 members; Location: New Delhi, India; Thanked: 130 times; GMAT Score:720

by rijul007 » Wed Nov 02, 2011 12:29 pm

Q1

lets say z = abc.lmn
we need the value of a..

Statement 1
10th digit of 100z is 2

100z = abclm.n
l=2
Insufficient

Statement 2
unit digit of 1000Z is 2
1000z = abclmn
n=2

Insufficient

Combinig 1 and 2
we get z = abc.2m2

Still Insufficient

Option E

Takeaway
You need to analyze what the ques is really asking for.
In this ques, u can rephrase the ques as
What is a?[if z=abc.lmn]

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rijul007: Legendary Member; Posts: 588; Joined: Sun Oct 16, 2011 9:42 amFollowed by: 9 members; Location: New Delhi, India; Thanked: 130 times; GMAT Score:720

by rijul007 » Wed Nov 02, 2011 12:36 pm

Q2

Is the hundredths digit of the decimal d greater than 5?
Rephrase it as
Is c>5? [d = abcxy.lmn]

Statement 1
the tenths digit of 10d is 7

10d = abcxyl.mn
y=7
Insufficient

Statement 2
the thousandths digit of d/10 is 7
a=7
Insufficient

Combining 1 and 2[/]
Insufficient

E

d/10 = abcx.ylmn

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mankey: Legendary Member; Posts: 627; Joined: Thu Jun 23, 2011 9:12 amFollowed by: 1 member; Thanked: 4 times

by mankey » Sun Nov 06, 2011 6:40 am

Someone please help on this one. This one is not clear.

Thanks.

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shankar.ashwin: Legendary Member; Posts: 966; Joined: Sat Jan 02, 2010 8:06 amFollowed by: 21 members; Thanked: 230 times

by shankar.ashwin » Sun Nov 06, 2011 9:15 am

What is the hundredth digit of the decimal Z?
1. The tenth digit of 100Z is 2
2. The unit digit of 1000Z is 2

First thing, you need to know what hundredth position actually means;

If you have a number say 123.456

Here note the decimal place value of each number,
1 - hundreds
2 - tens
3 - ones/units
4 - tenths
5 - hundredths
6 - thousandths (Notice whatever ends in 'ths' comes to the right of the decimal point)

In this problem, consider a number of the form A.BCD

hundredths is 'C' here;

we need to find 'C'

Statement 1;
tenth digit of 100Z is 2

100Z = ABC.D

tenth digit - D. We cannot find 'C' - insufficient

Statement 2:
1000Z - ABCD

unit digit of 1000Z is 2
unit digit - 'D'

Again this gives us 'D'. we cannot find 'C'.
Both statement actually give us the same value. Hence E IMO

mankey wrote:Someone please help on this one. This one is not clear.

Thanks.

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shankar.ashwin: Legendary Member; Posts: 966; Joined: Sat Jan 02, 2010 8:06 amFollowed by: 21 members; Thanked: 230 times

by shankar.ashwin » Sun Nov 06, 2011 9:21 am

Is the hundredths digit of the decimal d greater than 5?
(1) the tenths digit of 10d is 7.
(2) the thousandths digit of d/10 is 7.

Again consider a number of the form A.BCD.

hundredths place is 'C'

Statement 1
10d = AB.CD

tenths digit of 10d is 7 - C is 7, which is > 5. Sufficient

Statement 2
d/10 = 0.ABCD

the thousandths digit of d/10 is 7 - C is 7, which is > 5. Sufficient.

Both statements give you value of 'C' here. D IMO

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