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In a certain economy, C represents the total amount of [#permalink]
14 Dec 2012, 12:27

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Question Stats:

63% (02:00) correct
38% (01:33) wrong based on 32 sessions

In a certain economy, C represents the total amount of consumption in millions of dollars, Y represents the total national income in millions of dollars, and the relationship between these two values is given by the equation C=90+9Y/11. If the total amount of consumption in the economy increases by 99 million dollars, what is the increase in the total national income, in millions of dollars?

A.11 B.22 C.99 D.121 E.171

I tried several different approaches any tried to input numbers to see how it reacts but nothing worked... can someone care to explain?

Re: In a certain economy, C represents the total amount of [#permalink]
14 Dec 2012, 20:00

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This post received KUDOS

roygush wrote:

In a certain economy, C represents the total amount of consumption in millions of dollars, Y represents the total national income in millions of dollars, and the relationship between these two values is given by the equation C=90+9Y/11. If the total amount of consumption in the economy increases by 99 million dollars, what is the increase in the total national income, in millions of dollars?

A.11 B.22 C.99 D.121 E.171

I tried several different approaches any tried to input numbers to see how it reacts but nothing worked... can someone care to explain?

Re: In a certain economy, C represents the total amount of [#permalink]
15 Dec 2012, 02:07

MacFauz wrote:

roygush wrote:

In a certain economy, C represents the total amount of consumption in millions of dollars, Y represents the total national income in millions of dollars, and the relationship between these two values is given by the equation C=90+9Y/11. If the total amount of consumption in the economy increases by 99 million dollars, what is the increase in the total national income, in millions of dollars?

A.11 B.22 C.99 D.121 E.171

I tried several different approaches any tried to input numbers to see how it reacts but nothing worked... can someone care to explain?

Ok so your thinking process was - i need to find an increase hence subtract Yold and Ynew. I did isolated Y and then instead of C i put C+99 but wasnt aware that i should treat them as Old and New. interesting...

Re: In a certain economy, C represents the total amount of [#permalink]
15 Dec 2012, 04:54

Expert's post

roygush wrote:

In a certain economy, C represents the total amount of consumption in millions of dollars, Y represents the total national income in millions of dollars, and the relationship between these two values is given by the equation C=90+9Y/11. If the total amount of consumption in the economy increases by 99 million dollars, what is the increase in the total national income, in millions of dollars?

A.11 B.22 C.99 D.121 E.171

I tried several different approaches any tried to input numbers to see how it reacts but nothing worked... can someone care to explain?

Re: In a certain economy, C represents the total amount of [#permalink]
15 Dec 2012, 06:14

Expert's post

MacFauz wrote:

roygush wrote:

In a certain economy, C represents the total amount of consumption in millions of dollars, Y represents the total national income in millions of dollars, and the relationship between these two values is given by the equation C=90+9Y/11. If the total amount of consumption in the economy increases by 99 million dollars, what is the increase in the total national income, in millions of dollars?

A.11 B.22 C.99 D.121 E.171

I tried several different approaches any tried to input numbers to see how it reacts but nothing worked... can someone care to explain?

But also if we do :C = 90 + 9y/11 ------> adding 99 we have 11 (C - 90 +99)/9= y -------> 11C + 99/9 = Y clearly the only value that fits is 11 * 2 + 99/9 = y. That is, 121

Re: In a certain economy, C represents the total amount of [#permalink]
30 Jan 2014, 20:20

Expert's post

roygush wrote:

In a certain economy, C represents the total amount of consumption in millions of dollars, Y represents the total national income in millions of dollars, and the relationship between these two values is given by the equation C=90+9Y/11. If the total amount of consumption in the economy increases by 99 million dollars, what is the increase in the total national income, in millions of dollars?

A.11 B.22 C.99 D.121 E.171

I tried several different approaches any tried to input numbers to see how it reacts but nothing worked... can someone care to explain?

Given C = 90 + \frac{9Y}{11} Note that C changes whenever Y changes. So if C increases by 99, it's because Y increased from Y1 to Y2.

\frac{9}{11}(Y2 - Y1) = 99 Y2 - Y1 = 121 Y increased by 121 which led to an increase of 99 in C.