Problem Solving

AbeNeedsAnswers wrote:How do you calculate these fast?

Which of the following fractions is closest to 1/2?
A) 4/7
B) 5/9
C) 6/11
D) 7/13
E) 9/16

D

There can be few approaches to doing this faster. It depends on you at which approach you are comfortable. I am putting up my approach.

We have to find out which of the following number is closest to 1/2.

A number (1/2 + |a|) is closer to 1/2 than a number (1/2 + |b|) is closer to 1/2 if |a| < |b|.

Note that in the given fraction 1/2, the numerator '1' is half of the denominator '2,' so we would try to make the numerator half of the denominator with the given fractions in the options.

Let's take all the given fractions in the options.

A) 4/7 = (3.5 + 0.5)/7 = 3.5/7 + 0.5/7 = 1/2 + 1/14
B) 5/9 = (4.5 + 0.5)/9 = 4.5/9 + 0.5/9 = 1/2 + 1/18; since 1/18 < 1/14, 5/9 is relatively closer to 1/2, thus option A is ruled out.
C) 6/11 = (5.5 + 0.5)/11 = 5.5/11 + 0.5/11 = 1/2 + 1/22; since 1/22 < 1/18, 6/11 is relatively closer to 1/2, thus option B is ruled out.
D) 7/13 = (6.5 + 0.5)/13 = 6.5/13 + 0.5/13 = 1/2 + 1/26; since 1/26 < 1/18, 7/13 is relatively closer to 1/2, thus option C is ruled out.
E) 9/16 = (8 + 1)/16 = 8/16 + 1/16 = 1/2 + 1/16; since 1/16 > 1/26, 7/13 is relatively close to 1/2, thus option E is ruled out.

The correct answer: D

Hope this helps!

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-Jay
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AbeNeedsAnswers wrote:How do you calculate these fast?

Which of the following fractions is closest to 1/2?
A) 4/7
B) 5/9
C) 6/11
D) 7/13
E) 9/16

D

Another approach: Calculate the values in decimals. Though it is time-consuming, it is not necessarily always.

Convert all the fractions in percents.

Thus, 1/2 = (1/2)*100% = 50%.

Let's take all the options.

A) 4/7 = (4/7)*100% = (400/7)% = (57.1...)%
B) 5/9 = (5/9)*100% = (500/9)% = (55.55...)%. Since 55.55...% is relatively closer to 50% than 57.1...% is, Option A is ruled out.
C) 6/11 = (6/11)*100% = (600/11)% = (54.5...)%. Since 54.5...% is relatively closer to 50% than 55.55...% is, Option B is ruled out.
D) 7/13 = (7/13)*100% = (700/13)% = (53....)%. Since 53...% is relatively closer to 50% than 54.5..% is, Option C is ruled out.
E) 9/16 = (9/16)*100% = (900/16)% = (56...)%. Since 56...% is NOT relatively closer to 50% than 53...% is, Option E is ruled out.

The correct answer: D

Hope this helps!

Download free ebook: Manhattan Review GMAT Quantitative Question Bank Guide

-Jay
_________________
Manhattan Review GMAT Prep

Locations: New York | Barcelona | Manila | Melbourne | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.

AbeNeedsAnswers wrote:How do you calculate these fast?

Which of the following fractions is closest to 1/2?
A) 4/7
B) 5/9
C) 6/11
D) 7/13
E) 9/16

D

We can use a property of fractions that says "the greater the denominator, the smaller the value of the fraction"
For example, 3/14 is smaller than 3/13 because 14 is greater than 13

Now let's check the answer choices...

A) 4/7
3.5/7 = 1/2. So, 4/7 is 0.5/7 away from 1/2
Since 0.5/7 = 1/14, we can say that 4/7 is 1/14 away from 1/2

B) 5/9
4.5/9 = 1/2. So, 5/9 is 0.5/9 away from 1/2
Since 0.5/9 = 1/18, we can say that 5/9 is 1/18 away from 1/2

C) 6/11
Using the same logic, we can say that 6/11 is 1/22 away from 1/2

D) 7/13
Likewise, 7/13 is 1/26 away from 1/2

E) 9/16
And 9/16 is 1/16 away from 1/2

Of the BLUE fractions, 1/26 is the SMALLEST
So, the correct answer is D

Cheers,
Brent

AbeNeedsAnswers wrote:How do you calculate these fast?

Which of the following fractions is closest to 1/2?
A) 4/7
B) 5/9
C) 6/11
D) 7/13
E) 9/16

To determine which answer choice is closest to 1/2, we can subtract 1/2 from each answer choice. The difference that is closest to zero will indicate the fraction that is closest to 1/2.

A) 4/7

4/7 - 1/2 = 8/14 - 7/14 = 1/14

B) 5/9

5/9 - 1/2 = 10/18 - 9/18 = 1/18

C) 6/11

6/11 - 1/2 = 12/22 - 11/22 = 1/22

D) 7/13

7/13 - 1/2 = 14/26 - 13/26 = 1/26

E) 9/16

9/16 - 1/2 = 9/16 - 8/16 = 1/16

Since 1/26 is closest to zero, 7/13 is closest to 1/2.

Answer: D

Hi All,

We’re asked which of the following fractions is CLOSEST to ½. There are a number of different ways to approach the Arithmetic in this question (and you can use the given fractional answers or convert them to decimals).

Since the numerator of each answer is MORE than half of the denominator, we know that each fraction is GREATER than ½. Thus, we can look for how much greater each fraction is relative to ½ and define which is closest to that fraction.

Answer A: 4/7…. 3.5/7 is exactly ½, so this fraction is .5/7 = 1/14 greater than 1/2
Answer B: 5/9…. 4.5/9 is exactly ½, so this fraction is .5/9 = 1/18 greater than 1/2
Answer C: 6/11…. 5.5/11 is exactly ½, so this fraction is .5/11 = 1/22 greater than 1/2
Answer D: 7/13…. 6.5/13 is exactly ½, so this fraction is .5/13= 1/26 greater than 1/2
Answer E: 9/16…. 8/16 is exactly ½, so this fraction is .1/16 greater than 1/2

The smallest fraction ‘greater than ½’ is the one that’s closest to 1/2

Final Answer: D

GMAT Assassins aren’t born, they’re made,
Rich