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Re: What is the ratio of a to b to c ? [#permalink]
28 Apr 2013, 11:37

Zarrolou wrote:

What is the ratio of a to b to c ?

a/b/c=\frac{a}{bc}

I don't think that this is correct ?! all we know is the ratio of a to b is a/b .. that's why you must assign a new variable x and refer to it as smyarga did

It is the correct way to do this _________________

KUDOS is the good manner to help the entire community.

"If you don't change your life, your life will change you"

Re: What is the ratio of a to b to c ? [#permalink]
28 Apr 2013, 11:48

Rock750 wrote:

I don't think that this is correct ?! all we know is the ratio of a to b is a/b .. that's why you must assign a new variable x and refer to it as smyarga did

It is the correct way to do this

My point is : the ratio a to b is a division a/b The ration a to b is 2 means a/b=2 the ration (a to b) to c is also a division (I don't see why it sould not be). That's why I do not agree, maybe I have to review ratios Look at the real numbers , all respect A. a=20 , b= 80 c=50 a:b:c=1/200 a=8 , b=32 c=20 a:b:c=1/80 _________________

It is beyond a doubt that all our knowledge that begins with experience.

Re: What is the ratio of a to b to c ? [#permalink]
28 Apr 2013, 11:54

Zarrolou wrote:

Rock750 wrote:

I don't think that this is correct ?! all we know is the ratio of a to b is a/b .. that's why you must assign a new variable x and refer to it as smyarga did

It is the correct way to do this

My point is : the ratio a to b is a division a/b The ration a to b is 2 means a/b=2 the ration (a to b) to c is also a division (I don't see why it sould not be). That's why I do not agree, maybe I have to review ratios Look at the real numbers , all respect A. a=20 , b= 80 c=50 a:b:c=1/200 a=8 , b=32 c=20 a:b:c=1/80

in your opinion, why should ratio of a to b to c equal to (a to b) to c and not equal to a to (b to c) ? we don't know if the operation "to" is transitive .. _________________

KUDOS is the good manner to help the entire community.

"If you don't change your life, your life will change you"

Last edited by Rock750 on 28 Apr 2013, 12:28, edited 1 time in total.

Re: What is the ratio of a to b to c ? [#permalink]
28 Apr 2013, 11:59

Rock750 wrote:

in your opinion, why should ratio of a to b to c equal to (a to b) to c and not equal to a to (b to c) ? we don't know if the operation "to" is commutative ..

I think we are going nowhere here but in my opinion we should not forget the meaning of ratio: it's a division 5:5:5=0.2 is equal to (5:5):5=0,2 and not to 5:(5:5)=5 _________________

It is beyond a doubt that all our knowledge that begins with experience.

Re: What is the ratio of a to b to c ? [#permalink]
28 Apr 2013, 12:00

1

This post received KUDOS

Zarrolou, in your examples the ratio is the same. a=20 , b= 80 c=50 a:b:c=20:80:50=2:8:5 a=8 , b=32 c=20 a:b:c=8:32:20=2:8:5 You shouldn't mix them. Here is relative ratio of three numbers together. The ratio of three numbers a:b:c=n:m:k just means that there some integer x such that a=nx, b=mx, c=kx. _________________

I'm happy, if I make math for you slightly clearer And yes, I like kudos:)

Re: What is the ratio of a to b to c ? [#permalink]
28 Apr 2013, 12:02

Zarrolou wrote:

Rock750 wrote:

in your opinion, why should ratio of a to b to c equal to (a to b) to c and not equal to a to (b to c) ? we don't know if the operation "to" is commutative ..

I think we are going nowhere here but in my opinion we should not forget the meaning of ratio: it's a division 5:5:5=0.2 is equal to (5:5):5=0,2 and not to 5:(5:5)=5

the ratio of 5:5:5 is equal to 1:1:1 _________________

KUDOS is the good manner to help the entire community.

"If you don't change your life, your life will change you"

Re: What is the ratio of a to b to c ? [#permalink]
28 Apr 2013, 12:04

For example, the ratio of the number of women to the number of men to the number of children is 1 to 2 to 3. Your ratio as 1 to 80 is meaningless, because you compare 3 objects and as result have comparison of two objects. _________________

I'm happy, if I make math for you slightly clearer And yes, I like kudos:)

Re: What is the ratio of a to b to c ? [#permalink]
27 Jun 2013, 05:49

Rock750 wrote:

What is the ratio of a to b to c ?

(1) \frac{c}{a} =\frac{5}{2} and b=4a

(2) ac = 40 and b=16

st.1

a/c = 2/5, a/b = 1/4. to put these 3 in ratio we've to equate the common thing i.e. a. it'll become a/c=2/5 and a/b=2/8. << I equated a in both the expression by multiplying and dividing 2 a:b:c=2:8:5. simple.

st.2

It will clearly wont give the desired rsult. _________________

(1) \frac{c}{a} =\frac{5}{2} and b=4a. From b=4a, we have the \frac{a}{b}=\frac{1}{4}=\frac{2}{8}. So, we have that a:c=2:5 and a:b=2:8 --> a:b:c=2:8:5. Sufficient.

(2) ac = 40 and b=16. Not sufficient.

Answer: A.

As for your solution: the ratio is the same! You have a:b:c = a:4a:(2.5a) --> a reduces: a:b:c = 1:4:(2.5), which is the same ratio as a:b:c = 2:8:5 = 4:16:10 = 8:32:20 ...

Re: What is the ratio of a to b to c ? [#permalink]
27 Jun 2013, 08:19

First of all thank you members, But little confusion still remains, as long as I see this sum in isolation everything is clear but when I try and relate this sum to this sum given below I get a bit confused.

now in this sum individually obviously both are insufficient but when we take them together, expressing everything in terms of y

x = \frac {14}{y} z =\frac {21}{y}

so \,x:y:z = \frac {\frac{\frac{14}{y}}{y}}{\frac{21}{y}}

so \, for \, Y=1 \to x:y:z =\frac {\frac{14}{1}}{21}

and for \, Y=7 \to x:y:z =\frac {\frac{2}{7}}{3}

now using the same logic as above where we said "a reduces" and said that the ratio remains the same, can't we say in this sum too that ( x:y:z ) "Y reduces" hence 1+2 is sufficient to answer the ratio of x:y:z ?

if in a:b:c sum we say " as a:b:c = 2:8:5 = 4:16:10 = 8:32:20 ... " meaning in all the cases ratio is same

why in x:y:z = 14:1:21 and x:y:z = 2:7:3 , we are taking ratio to be different? shouldn't the ratio be same whether x:y:z= 14:1:21 or x:y:z = 2:7:3

we can say Y can be reduced and that 14:1:21 is the same as 2:7:3 answer should be C in this x:y:z sum, still here the answer is E. ?? Am I messing up something? Thanks.

Edit: my bad didn't see that 14:1:21 cannot be reduced to 2:7:3 so of course the answer is E _________________

- Stne

Last edited by stne on 02 Sep 2013, 23:03, edited 1 time in total.

Re: What is the ratio of a to b to c ? [#permalink]
27 Jun 2013, 08:29

1

This post received KUDOS

stne wrote:

First of all thank you members, But little confusion still remains, as long as I see this sum in isolation everything is clear but when I try and relate this sum to this sum given below I get a bit confused.

now in this sum individually obviously both are insufficient but when we take them together, expressing everything in terms of y

x = \frac {14}{y} z =\frac {21}{y}

so \,x:y:z = \frac {\frac{\frac{14}{y}}{y}}{\frac{21}{y}}

so \, for \, Y=1 \to x:y:z =\frac {\frac{14}{1}}{21}

and for \, Y=7 \to x:y:z =\frac {\frac{2}{7}}{3}

now using the same logic as above where we said "a reduces" and said that the ratio remains the same, can't we say in this sum too that ( x:y:z ) "Y reduces" hence 1+2 is sufficient to answer the ratio of x:y:z ?

if in a:b:c sum we say " as a:b:c = 2:8:5 = 4:16:10 = 8:32:20 ... " meaning in all the cases ratio is same

why in x:y:z = 14:1:21 and x:y:z = 2:7:3 , we are taking ratio to be different? shouldn't the ratio be same whether x:y:z= 14:1:21 or x:y:z = 2:7:3

we say say Y can be reduced and that 14:1:21 is the same as 2:7:3 answer should be C in this x:y:z sum, still here the answer is E. ?? Am I messing up something? Thanks.

Re: What is the ratio of a to b to c ? [#permalink]
27 Jun 2013, 08:51

@stunn3r

Thank you, equating the common variable seems to make sense , doing it my way where I was expressing everything in terms of a single variable , does not seem to work here. Thank you _________________

Re: What is the ratio of a to b to c ? [#permalink]
01 Jul 2014, 00:53

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