The tens digit of positive integer X is 3. Is the units : DS Archive
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# The tens digit of positive integer X is 3. Is the units

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The tens digit of positive integer X is 3. Is the units [#permalink]

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04 Jun 2008, 12:27
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The tens digit of positive integer X is 3. Is the units digit of X greater than 4?

1) the units digit if 2X is less than the units digit of X
2) the tens digit id 2X is7
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04 Jun 2008, 12:28
I made a typo in the 2nd condition. It should be

2) The tens digit of 2X is 7

Sorry
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04 Jun 2008, 12:38
D.

1 - tells us that the number has to be 36, 37, 38, or 39 all have units > 4. Simple to check 30 has same units, 31, 32, 33, 34 all have larger unit digits when multiplied by 2.

2 - tells us number must be 35 36 37 38 39 all lower would give us a 6 for a tens digit.

Last edited by lsuguy7 on 05 Jun 2008, 05:58, edited 1 time in total.
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04 Jun 2008, 19:58
puma wrote:
The tens digit of positive integer X is 3. Is the units digit of X greater than 4?

1) the units digit if 2X is less than the units digit of X
2) the tens digit id 2X is7

i will go with B

1)
2*X unit digit is less than X..

suppose x=30 or 35.. in both cases unit digit of 2X is less than 2..however 5>4 and 0<4
Insuff

2)
2*3X=7Y

X has to be greater than 5..which is >4 Sufficient
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04 Jun 2008, 20:12
D for me as well.

In case for X=30 the units digit of 2X i.e 0 is not less than the units digit of X.
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05 Jun 2008, 08:58
I'm saying D on this one folks. OA please?
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05 Jun 2008, 09:18
puma wrote:
The tens digit of positive integer X is 3. Is the units digit of X greater than 4?

1) the units digit if 2X is less than the units digit of X
2) the tens digit id 2X is7

D

1: must be 5,6,7,8,9 to hold.

2: must be, 35, 6,7,8,9 to hold.
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05 Jun 2008, 10:59
GMATBLACKBELT wrote:
puma wrote:
The tens digit of positive integer X is 3. Is the units digit of X greater than 4?

1) the units digit if 2X is less than the units digit of X
2) the tens digit id 2X is7

D

1: must be 5,6,7,8,9 to hold.

2: must be, 35, 6,7,8,9 to hold.

i dont get how A is sufficient..

supose X=30 or 35..

in both cases 2*X=60 or 70..so unit digit of 2X is 0..however unit digit of X is 5 or 0..so A is insuff..
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05 Jun 2008, 11:18
OA is D but I don't get why A is sufficient
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05 Jun 2008, 12:06
i get it..

jeez..

suppose X=10X+y

then 2X=20X+2Y 2y<y... then y=5, 6,7, 8, 9...

A is sufficient..
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05 Jun 2008, 23:50
Otherwise also, we cant take 30 because its not satisfying the first condition, so no confusion.
fresinha12 wrote:
GMATBLACKBELT wrote:
puma wrote:
The tens digit of positive integer X is 3. Is the units digit of X greater than 4?

1) the units digit if 2X is less than the units digit of X
2) the tens digit id 2X is7

D

1: must be 5,6,7,8,9 to hold.

2: must be, 35, 6,7,8,9 to hold.

i dont get how A is sufficient..

supose X=30 or 35..

in both cases 2*X=60 or 70..so unit digit of 2X is 0..however unit digit of X is 5 or 0..so A is insuff..
Re: DS:tens digit   [#permalink] 05 Jun 2008, 23:50
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