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I'm a bit confused. If they are added to 1:1 ratio, wouldn't the resulting num & denom always be 1 apart? I understand the fraction value decreases, but shouldn't the num and denom value difference stay constant?

Bunuel
Official Solution:

­
The ratio of two positive integers, \(m\) and \(n\), is 4 to 3. If the values of \(m\) and \(n\) are increased in a ratio of 1 to 1, which of the following cannot be the resulting integers?

I. 8 and 5

II. 25 and 21

III. 13 and 11


A. I only
B. II only
C. III only
D. I and II only
E. I and III only­


When two numbers are increased in a ratio of 1:1, it implies that the same positive number was added to both of them.

If a fraction is between 0 and 1, adding the same positive number to both the numerator and denominator increases the value of the fraction. For instance, if we add 2 to the numerator and denominator of \(\frac{1}{3}\), we get \(\frac{1 + 2}{3 + 2} = \frac{3}{5}\), which is greater than the initial fraction of \(\frac{1}{3}\).

If a fraction is more than 1, adding the same positive number to both the numerator and denominator decreases the value of the fraction. For instance, if we add 2 to the numerator and denominator of \(\frac{3}{2}\), we get \(\frac{3 + 2}{2 + 2} = \frac{5}{4} = 1.25\), which is less than the initial fraction of \(\frac{3}{2} = 1.5\).

For the question at hand, the original ratio was 4:3, which is more than 1 (≈1.3), thus adding the same positive number to both the numerator and the denominator will decrease the value of the new ratio, bringing it closer to, but still above 1. Therefore, both 25 and 21 (\(\frac{25}{21} \approx 1.2\)), and 13 and 11 (\(\frac{13}{11} \approx 1.2\)), are possible values for the resulting integers since their ratio is less than 1.3, while 8 to 5 cannot be the resulting integers, as their ratio is 1.6, which is greater than 1.3.


Answer: A


Given that the ratio of two positive integers is 4 to 3, the numbers could be 4 and 3, 8 and 6, 12 and 9, and so on. When the original numbers are increased in a ratio of 1:1, the difference between the resulting numbers will remain the same as it was initially. For example, if the initial numbers were 4 and 3 (difference of 1), the difference after the increase will still be 1. However, if the initial numbers were 40 and 30 (difference of 10), the difference in the resulting numbers would also remain 10, not 1.

Does this make sense?
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Yes, I get it now. Thank you.
Bunuel
Moh12345
I'm a bit confused. If they are added to 1:1 ratio, wouldn't the resulting num & denom always be 1 apart? I understand the fraction value decreases, but shouldn't the num and denom value difference stay constant?

Bunuel
Official Solution:

­
The ratio of two positive integers, \(m\) and \(n\), is 4 to 3. If the values of \(m\) and \(n\) are increased in a ratio of 1 to 1, which of the following cannot be the resulting integers?

I. 8 and 5

II. 25 and 21

III. 13 and 11


A. I only
B. II only
C. III only
D. I and II only
E. I and III only­


When two numbers are increased in a ratio of 1:1, it implies that the same positive number was added to both of them.

If a fraction is between 0 and 1, adding the same positive number to both the numerator and denominator increases the value of the fraction. For instance, if we add 2 to the numerator and denominator of \(\frac{1}{3}\), we get \(\frac{1 + 2}{3 + 2} = \frac{3}{5}\), which is greater than the initial fraction of \(\frac{1}{3}\).

If a fraction is more than 1, adding the same positive number to both the numerator and denominator decreases the value of the fraction. For instance, if we add 2 to the numerator and denominator of \(\frac{3}{2}\), we get \(\frac{3 + 2}{2 + 2} = \frac{5}{4} = 1.25\), which is less than the initial fraction of \(\frac{3}{2} = 1.5\).

For the question at hand, the original ratio was 4:3, which is more than 1 (≈1.3), thus adding the same positive number to both the numerator and the denominator will decrease the value of the new ratio, bringing it closer to, but still above 1. Therefore, both 25 and 21 (\(\frac{25}{21} \approx 1.2\)), and 13 and 11 (\(\frac{13}{11} \approx 1.2\)), are possible values for the resulting integers since their ratio is less than 1.3, while 8 to 5 cannot be the resulting integers, as their ratio is 1.6, which is greater than 1.3.


Answer: A


Given that the ratio of two positive integers is 4 to 3, the numbers could be 4 and 3, 8 and 6, 12 and 9, and so on. When the original numbers are increased in a ratio of 1:1, the difference between the resulting numbers will remain the same as it was initially. For example, if the initial numbers were 4 and 3 (difference of 1), the difference after the increase will still be 1. However, if the initial numbers were 40 and 30 (difference of 10), the difference in the resulting numbers would also remain 10, not 1.

Does this make sense?
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I like the solution - it’s helpful. And not to mention, it's a super conceptual question!
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I applied this logic - Num - 4x+ a and Denom 4x + b so try values from options ii) satisfied for x = 4 and a = 6 iii) satisfied for x = 2 and a = 5. Only option i) is not satisfied for positive values of x and a. Is my approach correct?
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I applied this logic - Num - 4x+ a and Denom 4x + b so try values from options ii) satisfied for x = 4 and a = 6 iii) satisfied for x = 2 and a = 5. Only option i) is not satisfied for positive values of x and a. Is my approach correct?
I think your setup is not precise. Also, you didn’t actually prove that (I) fails.
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Pls help me understand,
We can write
initially, m = 4a & n = 3a.
Later,
m = 4a + b,
n = 3a + b

Given m & n are integers, a & b will also be integers. Trying out different values of a&b for each option:
I) no possible a & b
II) 25 = 4*4 + 4 , 21 = 3*4 + 4
III) no possible a & b

So answer should be both 1 & 3 ?
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Bunuel
Official Solution:

­
The ratio of two positive integers, \(m\) and \(n\), is 4 to 3. If the values of \(m\) and \(n\) are increased in a ratio of 1 to 1, which of the following cannot be the resulting integers?

I. 8 and 5

II. 25 and 21

III. 13 and 11


A. I only
B. II only
C. III only
D. I and II only
E. I and III only­


When two numbers are increased in a ratio of 1:1, it implies that the same positive number was added to both of them.

If a fraction is between 0 and 1, adding the same positive number to both the numerator and denominator increases the value of the fraction. For instance, if we add 2 to the numerator and denominator of \(\frac{1}{3}\), we get \(\frac{1 + 2}{3 + 2} = \frac{3}{5}\), which is greater than the initial fraction of \(\frac{1}{3}\).

If a fraction is more than 1, adding the same positive number to both the numerator and denominator decreases the value of the fraction. For instance, if we add 2 to the numerator and denominator of \(\frac{3}{2}\), we get \(\frac{3 + 2}{2 + 2} = \frac{5}{4} = 1.25\), which is less than the initial fraction of \(\frac{3}{2} = 1.5\).

For the question at hand, the original ratio was 4:3, which is more than 1 (≈1.3), thus adding the same positive number to both the numerator and the denominator will decrease the value of the new ratio, bringing it closer to, but still above 1. Therefore, both 25 and 21 (\(\frac{25}{21} \approx 1.2\)), and 13 and 11 (\(\frac{13}{11} \approx 1.2\)), are possible values for the resulting integers since their ratio is less than 1.3, while 8 to 5 cannot be the resulting integers, as their ratio is 1.6, which is greater than 1.3.


Answer: A
Pls help me understand,
We can write
initially, m = 4a & n = 3a.
Later,
m = 4a + b,
n = 3a + b

Given m & n are integers, a & b will also be integers. Trying out different values of a&b for each option:
I) no possible a & b
II) 25 = 4*4 + 4 , 21 = 3*4 + 4
III) no possible a & b

So answer should be both 1 & 3 ?

This is why the logical approach shown in the solution is more reliable. You're testing different values for each option, but that method risks missing valid cases. For example, for III, if you take m = 8, n = 6, and b = 5, it works, so III is actually possible.
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Bunuel bb if you could throw some light on this approach..if this is fine or not?


I. 8 and 5

4a + b/3a+b = 8/5

20a + 5b = 24a +8b
-4a=3b
s=-3b/4..Invalid

Its coming in negative....Not possible...

II
25 and 21

(4a + b)/(3a+b) = 25/21

84a + 21b = 75a+25b
9a = 4b
a=4b/9...Positive and valid

III 13 and 11

(4a + b)/(3a+b) = 13/11
44a + 11b = 39a + 13b
5a= 2b
a=2/5b ..Positive..Valid....
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Aboyhasnoname
Bunuel bb if you could throw some light on this approach..if this is fine or not?


I. 8 and 5

4a + b/3a+b = 8/5

20a + 5b = 24a +8b
-4a=3b
s=-3b/4..Invalid

Its coming in negative....Not possible...

II
25 and 21

4a + b/3a+b = 25/21

84a + 21b = 75a+25b
9a = 4b
a=4b/9...Positive and valid

III 13 and 11

4a + b/3a+b = 13/11
44a + 11b = 39a + 13b
5a= 2b
a=2/5b ..Positive..Valid....

When you discard the first option, the reasoning looks fine. However, what I don’t follow is how you go from something like 9a = 4b straight to saying that 25:21 is achievable. That link feels missing in your explanation.

P.S. Also, in your solution some necessary brackets are missing, which makes following your intended meaning harder.
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Thanks Bunuel . Have edited it. Regarding the explanation....I actually didn't know how to solve..tried this..the first one seemed odd one out so i marked that :shh::shh:...

However, thinking deeper...we can do like this also right.....?
Let b be the added number....

8 - 4a = 5-3a = b
a=3
then b = -4..negative not possible


II
25 - 4a = 21 - 3a = b
a = 4
b = 9..valid...


III. 13-4a = 11- 3a = b
a = 2
b = 5 Valid....





Bunuel


When you discard the first option, the reasoning looks fine. However, what I don’t follow is how you go from something like 9a = 4b straight to saying that 25:21 is achievable. That link feels missing in your explanation.

P.S. Also, in your solution some necessary brackets are missing, which makes following your intended meaning harder.
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How I thought
4k+y/3k+y is new fraction = 3k+y/3k+y + k/3k+y
= 1+ ~1/3
So therefore whatever amount after 1 should be less than 1/3 - if yes there is potential for it to be answer. And II and IIi both satisfy this so answer is I (cannot be possible)
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