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Re: The monthly incomes of A and B are in the ratio 3 : 2, and t [#permalink]
Expert Reply
The answer is A Sir NOT D
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Re: The monthly incomes of A and B are in the ratio 3 : 2, and t [#permalink]
There is a similar question 5 questions back on previous page,same situation.

How can it be A?ratios can be anything

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Re: The monthly incomes of A and B are in the ratio 3 : 2, and t [#permalink]
4
vaishar3 wrote:
There is a similar question 5 questions back on previous page,same situation.

How can it be A?ratios can be anything

Posted from my mobile device


I agree with that, however, in this case, there are several ingredients that allows finding a pattern which is always true:

Let's suppose that the relation between the total income of A and B can be written as:

\(3x + 2x = I\), with \(I = A_{I} + B_{I}\)
In this case, the total income of \(A\) and \(B\) are given by:
\(A_{I} = \frac{3*I}{5}\)
\(B_{I} = \frac{2*I}{5}\)
And the total expenditures: (\(E\))
\(4y + 3y = E\), with \(E = A_{E} + B_{E}\)
that could be written as:
\(A_{E} = \frac{4*E}{7}\)
\(B_{E} = \frac{3*E}{7}\)
Now, for each person, we will calculate their savings equation:
\(A_{S} = \frac{3*I}{5}-\frac{4*E}{7}\)
\(B_{S} = \frac{2*I}{5}-\frac{3*E}{7}\)
In order to work with friendly numbers, we are going to multiply each equation by 35:
\(35*A_{S} = 21*I-20*E\)
\(35*B_{S} = 14*I-15*E\)
Now, we can substract both equations:
\(35*A_{S} - 35*B_{S} = 21*I-14*I - 20*E-15*E\)
Solving:
\(35*A_{S} - 35*B_{S} = 7*I - 5*E\)
(the following step is not necessary)
\(A_{S} - B_{S} = \frac{7*I - 5*E}{35}\)
In this case, we now that I>E (they told us), therefore, this expression \(7*I - 5*E\) is always positive. Finally, we can say that no matter what kind of numbers do you pick, the savings of A will be always greater than B.
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The monthly incomes of A and B are in the ratio 3 : 2, and t [#permalink]
Savings Of A=3x-2y
Savings of B=2x-3y
Using these equations If I take x=10 and y=5
Savings of A=5
Savings of B=5
In this case ans is C
But for x=5 and y=2
Savings of A>savings of B
Ans is A for this case
So shouldn’t be D is the ans?

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Re: The monthly incomes of A and B are in the ratio 3 : 2, and t [#permalink]
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OE

Let the income of A and B be 3s and 2s, respectively, and let their expenditures be 4t and 3t. Then since savings is defined as income minus expenditure, Column A = the saving of A = 3s – 4t, and Column B =
saving of B = 2s – 3t.

Column A is greater than Column B when 3s – 4t > 2s – 3t, or s > t.

Since money is positive, s and t are positive. Since income is greater than expenditure (given), the Income of B = 2 s > Expenditure of B = 3 t. Hence, s > 3 t/2. Clearly, s > t. Since we know that Column A >

Column B when s > t, the answer is (A)
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Re: The monthly incomes of A and B are in the ratio 3 : 2, and t [#permalink]
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Re: The monthly incomes of A and B are in the ratio 3 : 2, and t [#permalink]
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