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18 Nov 2015, 20:34
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Attached. Much obliged!
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Can anyone please explain this math problem? [#permalink]
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18 Nov 2015, 21:18
porkery wrote: Attached. Much obliged! Hi, lets see what all we have.. 1) year 1999.. number of students=5500 number of faculty=5500/R.. 2) year 2004..... number of students=5500(100S)/100..where S is the % change over 5 academic years number of faculty=5500/R*(100+F)/100..where F is the % change over 5 academic years.. so number of students/number of faculty members= [5500(100S)/100]/[5500/R*(100+F)/100] =(100S)/(100+F) * R ans D
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Re: Can anyone please explain this math problem? [#permalink]
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17 Sep 2016, 02:34
chetan2u wrote: porkery wrote: Attached. Much obliged! number of students=5500(100S)/100..where S is the % change over 5 academic years number of faculty=5500/R*(100+F)/100..where F is the % change over 5 academic years.. Hi chetan2u, Can you please tell me how you got the below step ? 100S and 100+F .. chetan2u wrote: number of students=5500(100S)/100..where S is the % change over 5 academic years number of faculty=5500/R*(100+F)/100..where F is the % change over 5 academic years..
i din understand from where 100 came all of a sudden.. is there anything i am missing ? just a query, is the answer (100S)/(100+F) * R ? cause the one mentioned in screenshot is different.
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17 Sep 2016, 04:55
Shrivathsan wrote: chetan2u wrote: porkery wrote: Attached. Much obliged! number of students=5500(100S)/100..where S is the % change over 5 academic years number of faculty=5500/R*(100+F)/100..where F is the % change over 5 academic years.. Hi chetan2u, Can you please tell me how you got the below step ? 100S and 100+F .. chetan2u wrote: number of students=5500(100S)/100..where S is the % change over 5 academic years number of faculty=5500/R*(100+F)/100..where F is the % change over 5 academic years..
i din understand from where 100 came all of a sudden.. is there anything i am missing ? just a query, is the answer (100S)/(100+F) * R ? cause the one mentioned in screenshot is different. Hi, There is a decrease in the number of students, say s%... Then the student who were initially 5500 goes down to 5500*(100s)/100.. Example.. the decrease was 20%, so number is 5500*(10020)/100=5500*80/100.. Similarly for increase in faculty (100+F)/100..
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Re: Can anyone please explain this math problem? [#permalink]
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17 Sep 2016, 09:43
chetan2u wrote: Hi, There is a decrease in the number of students, say s%... Then the student who were initially 5500 goes down to 5500*(100s)/100.. Example.. the decrease was 20%, so number is 5500*(10020)/100=5500*80/100.. Similarly for increase in faculty (100+F)/100..
Thank you so much chetan2u for your explanation Kudos to you .. But the answer given is (100+S)/(100+F) * R Since Students decrease, it should be 100s right ?
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27 Sep 2016, 13:57
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Shrivathsan wrote: But the answer given is (100+S)/(100+F) * R
Since Students decrease, it should be 100s right ? I think the process used is completely right, but there is a minor flaw. S represents the change and not the decrease itself. The change has to be used as +S, and when the change is on the negative side (there is a decrease), S will assume a ve value. Example: If there is an increase, S = +5%, or in case of decrease, S = 7% Over here in the working provided, in case of increase, S = 5% and in case of decrease, S = 7%. The general way of depiction is wrong. Working is totally fine though. Hope it helps

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29 Sep 2016, 06:11
testprepabc wrote: The general way of depiction is wrong.
Thanks testprepabcBut they have provided S is decreasing right ? Since the value is not given .. we are giving a general expression ?
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Re: Can anyone please explain this math problem? [#permalink]
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01 Oct 2016, 01:08
Shrivathsan wrote: But they have provided S is decreasing right ? Since the value is not given .. we are giving a general expression ? The question defines S to be a percentage change in the number of students. We need a formula which will generalize both the increase and the decrease. Hence the positive sign. Small example: Let's say the question had 2 parts  One with a x% increase and the other with a x% decrease. The easiest way to answer this is to write a formula which will satisfy both the equation instead of writing 2 formulae one with +S and the other with S. Rather you would probably write a formula with +S and replace +S = x% for increase and +S = x% for decrease. A mathematical corollary would be formula for compound interest. We do not change the +ve sign in the bracket to ve for decreasing Rs in A=P[1+(R/100)]^n, rather replace R with a ve value. Remember, formulae should be general and conventional. Hope this explains and helps you

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