rosyneha wrote:My question is first digit of the number is the digit in the unit's place or ten's place?

I think first digit means first from the left, i.e. in this case the digit in ten's place.
And the answer choices confirms what I think as all of them are odd.


Let us assume the number is XY, where X and Y are ten's and unit's digit respectively.

As the original number is even, Y must be even.
The reversed number YX is odd, so the X must be odd.

Now, YX > XY
So, X must be less than Y.
Now, Y cannot be greater than 8.
So, X must be less than 8.

Answer : E

It has to be the tens digit as the ones digit must be even... E is the answer.

Now, YX > XY
So, X must be less than Y.
Now, Y cannot be greater than 8.
So, X must be less than 8.

[/quote]Now, YX > XY
So, X must be less than Y.
Now, Y cannot be greater than 8.
So, X must be less than 8.

Hi,

I figured the answer out but while looking at the explanation, I dont understand why X must be less than Y.

Can you please explain?

Thanks

Hi,

I figured the answer out but while looking at the explanation, I dont understand why X must be less than Y.

Now, YX > XY
So, X must be less than Y.
Now, Y cannot be greater than 8.
So, X must be less than 8.

Can you please explain?

Thanks

TG_GMAT wrote:...but while looking at the explanation, I dont understand why X must be less than Y.

If a 2-digit integer (Say, M) is less than another 2-digit integer (Say, N), then the ten's digit of M cannot be greater than the ten's digit of N. For example, 12 is less than 21, 1 < 2 or 34 is less than 43, 3 < 4 or 24 < 28 and 2 is not greater than 2.

So, in general if XY < YX, then X cannot be greater than Y, i.e. X ≤ Y
As in this case X is an odd integer and Y is an even integer, X cannot be equal to Y.
So, X < Y

Hope that helps.

Great, that helps. Thanks.

pick some numbers using the answer choices and eliminate those that violate the definition.

Even < odd
(A)1-12 or 21 eliminate
(B)3-38 or 83 eliminate
(C)5-58 or 85 eliminate
(D)7-78 or 87 eliminate
(E)9. correct answer.