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In the decimal 3.1de

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In the decimal 3.1de

by Needgmat » Sat Oct 01, 2016 8:41 pm
In the decimal 3.1de, d and e each represent a digit. If represent the decimal 3.1de rounded to the nearest tenth, what is the value of x?

1) d=4

2) e=8

OAA

please check and advise, what I am missing

Statement 1) d=4

3.14e, e can be any digit.

If I put e = 2, then 3.142 -- rounded nearest hundred is 3.14 and rounded nearest tenth is 3.1

If I put e= 8, then 3.148 -- rounded nearest hundred is 3.15. So wouldn't be nearest tenth either 3.1 or 3.2?

Please explain why this is sufficient.

Thanks,

Kavin
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by GMATGuruNY » Sun Oct 02, 2016 3:55 am
Needgmat wrote:In the decimal 3.1de, d and e each represent a digit. If x represents the decimal 3.1de rounded to the nearest tenth, what is the value of x?

1) d=4

2) e=8
The following range will yield 3.1 when rounded to the nearest tenth:
3.05 ≤ 3.1de < 3.15.
Any value less than 3.15 -- even 3.149 -- is rounded DOWN to 3.1, with the result that x = 3.1.

The following range will yield 3.2 when rounded to the nearest tenth:
3.15 ≤ 3.1de ≤ 3.199.
Any value within this range is rounded UP to 3.2, with the result that x = 3.2.

Statement 1:
decimal = 3.14e.
Since 3.14e is within the range in red, x = 3.1.
SUFFICIENT.

Statement 2:
decimal = 3.1d8.
If d=4, then 3.148 is within the range in red, with the result that x = 3.1.
If d=5, then 3.158 is within the range in blue, with the result that x = 3.2.
INSUFFICIENT.

The correct answer is A.
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by Needgmat » Sun Oct 02, 2016 6:21 am
The following range will yield 3.1 when rounded to the nearest tenth:
3.05 ≤ 3.1de < 3.15.
Any value less than 3.15 -- even 3.149 -- is rounded DOWN to 3.1, with the result that x = 3.1.

The following range will yield 3.2 when rounded to the nearest tenth:
3.15 ≤ 3.1de ≤ 3.199.
Any value within this range is rounded UP to 3.2, with the result that x = 3.2.

Statement 1:
decimal = 3.14e.
Since 3.14e is within the range in red, x = 3.1.
SUFFICIENT.

Statement 2:
decimal = 3.1d8.
If d=4, then 3.148 is within the range in red, with the result that x = 3.1.
If d=5, then 3.158 is within the range in blue, with the result that x = 3.2.
INSUFFICIENT.

The correct answer is A.
Hi GMATGuruNY ,

Thank you so much for your reply.

Just a quick question. If we have 3.15 and we have to round nearest tenth then will t be 3.2 or 3.1?

Please advise sir.

Many thanks in advance

Kavin
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by [email protected] » Sun Oct 02, 2016 9:40 am
Hi Kavin,

When using 'rounding rules', the digits 0-4 require that you round DOWN and the digits 5-9 require that you round UP.

Thus, 3.15 rounded to the nearest TENTH would be 3.2 (since we have a 5 as the hundredths digit).

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by ceilidh.erickson » Sun Oct 02, 2016 2:04 pm
Needgmat wrote: please check and advise, what I am missing

Statement 1) d=4

3.14e, e can be any digit.

If I put e = 2, then 3.142 -- rounded nearest hundred is 3.14 and rounded nearest tenth is 3.1

If I put e= 8, then 3.148 -- rounded nearest hundred is 3.15. So wouldn't be nearest tenth either 3.1 or 3.2?

Please explain why this is sufficient.

Thanks,

Kavin
I think I understand your confusion. When we round, it's not a multi-step process - we don't go out to the furthest digit we have and round up each one like a domino effect until we get to the digit we want. We only look ONE digit further than the one we want.

Whether we have 3.142 or 3.148, we only look at the hundredths digit (the 4) when we're rounding to the tenths digit. The thousandths digit is irrelevant.
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by Brent@GMATPrepNow » Sun Oct 02, 2016 2:55 pm
In The decimal 3.1de, d and e each represent a digit. If X represents the decimal 3.1de rounded to the nearest tenth, what is the value of x?
1) D=4
2) E=8
Target question: What is the value of x?

Given: X represents the decimal 3.1de rounded to the nearest tenth

Statement 1: D = 4
So, the decimal could by 3.140, 3.141, 3.142, 3.143, 3.144, 3.145, 3.146, etc
To round any of these decimals to the nearest tenth, we need only check the hundredths digit.
Since the hundredths digit is 4, ALL of these decimals round to be 3.1
In other words, X must equal 3.1
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: E=8
There are several different decimals that meet this condition. Here are two:
Case a: the numbers decimal is 3.128, in which case X = 3.1
Case b: the numbers decimal is 3.168, in which case X = 3.2
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer = A

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by GMATGuruNY » Mon Oct 03, 2016 1:57 am
Needgmat wrote:Hi GMATGuruNY ,

Thank you so much for your reply.

Just a quick question. If we have 3.15 and we have to round nearest tenth then will t be 3.2 or 3.1?

Please advise sir.

Many thanks in advance

Kavin
If we move from left to right on a number line, we round UP as soon as we reach the HALFWAY POINT between two values.
Otherwise, we round DOWN.
3.1-----3.15-----3.2-----3.25-----3.3
Moving left to right on the number line above, we reach the halfway point between 3.1 and 3.2 when we reach 3.15.
We reach the halfway point between 3.2 and 3.3 when we reach 3.25.
As a result, the two ranges in blue are rounded UP, while the two ranges in red are rounded DOWN.
As you can see, 3.15 -- the halfway point between 3.1 and 3.2 -- is rounded UP to 3.2.
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