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Doubts regarding ratio topic in quantitative analysis

Sohil (Learner) (631 Points)

18 October 2011

In the exercise provided on page 6 of the topic ratio ,proportions,indices and logarithms.

https://220.227.161.86/19646chapter-1.pdf

Answer for question 10 is shown as option c which is 2/27.

But according to me it should be 2/21 hence option d i correct answer.

So am i wrong or its printed wrong or i miscalculated it.

Also how to get answer of question number 21?

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5 Replies

(Guest)

Hi,

you r right for 10Th question.

answer is 2:21

for 21 st question,

(2s-p)^2:(3t-p)^2=2s:3t it means(2s-p)^2/(3t-p)^2=2s/3t,use (a-b)^2=a^2+b^2-2ab,u get

(4s^2+p^2-4sp/9t^2+p^2-6tp)=2s/3t,do the cross multiplication

12ts^2+3tp^2-12spt=18st^2+2sp^2-12spt

12ts^2-18st^2=2sp^2-3tp^2

6st(2s-3t)=p^2(2s-3t)

6st=p^2

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Sohil (Learner) (631 Points)
Replied 18 October 2011

Thanks sunitha. For question 21 i also followed same step but because of my carelessness i left in middle thinking it wont be that way. I am happy i choosed the correct concept but need to avoid carelessness and be confident on self. Thanks again.

avinash (none) (21 Points)
Replied 31 October 2011

anyone know how to solve qustion no. 20 in this exercise?

CA D. Singhal (CA ) (490 Points)
Replied 31 October 2011

@ avinash: Yes, Q.20 is damn easy once you know the concept behind "Sub Duplicate Ratio",
For clarity, consider this- Sub duplicate ratio of a is a^{1/2}

Now according to Q. and above concept the equation becomes -

p^{2}/ q^{2} = [ p - x^{2}]/ [q - x^{2}]

After cross multiplication it becomes;

p^{2}q - p^{2}x^{2} = pq^{2} - q^{2}x^{2}

x^{2}[ p^{2} - q^{2} ] = p^{2}q - pq^{2}

After keeping x^{2} in LHS, we get;

x^{2} = [pq(p-q ] / [(p-q)(p+q)]

x^{2} = pq/(p+q)

Since this is not given in any of the options; answer is (d) that is None Of These

Hope you have got the concept and the problem

Sohil (Learner) (631 Points)
Replied 04 November 2011

One doubt regarding proportion solved example number 3 regarding tea powder.

I find it wrongly solved.

Same pdf page 11.

it states profit is 17.5%.So if cost is 100 than 117.5 is sp and 17.5 is profit on it.

What they did is sp is 100 and 17.5 as profit.whereas 17.5 is percentage not amount and if cp is 85.1 than only sp can become 100 with 17.5 percent profit.

Am i right?