Last year, all registered voters in Kumannia voted either for the Revolutionary Party
or for the Status Quo Party. This year, the number of Revolutionary voters increased
10%, while the number of Status Quo voters increased 5%. No other votes were cast.
If the number of total voters increased 8%, what fraction of voters voted Revolutionary
this year?
Source-MGMAT Guide 1
Am trying to solve this through allegations:
5%(S)_________8%______10%(R)
So,5%(S)____2x____8%___3x___10%(R)
R/Total=3/5*100=60%
But correct ans is 61.1
Someone please guide me where am i making a mistake.
Weighted avg with % change
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- Atekihcan
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According to your solution, you have determined the ratio of R to (S + R), where S and R are number of voters for Status Quo and Revolutionary party for the last year. But the problem asked for the ratio for this year.arpshriv wrote:...what fraction of voters voted Revolutionary this year?
This year number of voters for Revolutionary party = R + 10% of R = 1.10*R
And, number of total voters = (R + S) + 8% of (R + S) = 1.08*(R + S)
So, required ratio = (1.10*R)/(1.08*(R + S)) = (1.10/1.08)*(R/(S + R)) = (1.10/1.08)*(3/5) = (55/54)*(3/5) = 11/18
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This is a WEIGHTED AVERAGE/MIXTURE problem.Aishwarya1204 wrote:Last year all registered voters either voted for the Revolutionary party or the Status Quo party. This year the number of revolutionary voters increased by 10% and the Status Quo voters increased by 5%. No other votes were cast. If the number of total votes increased by 8%. What fraction of voters voted for the Revolutionary party this year.
Answer is [spoiler] 11/18 [/spoiler]
Let R = Revolutionary voters and S = Status Quo voters.
Increase in R = 10%.
Increase in S = 5%.
Increase in the MIXTURE of R+S = 8%.
To determine the ratio of R to S in the mixture, use ALLIGATION.
Step 1: Plot the 3 percentages on a number line, with the percentage increases for R and S (10% and 5%) on the ends and the percentage increase for the mixture (8%) in the middle.
R (10%)------------8%------------(5%) S
Step 2: Calculate the distances between the percentages.
R (10%)-----2-----8%-----3-----(5%) S
Step 3: Determine the ratio in the mixture.
The required ratio of R to S is equal to the RECIPROCAL of the distances in red:
R:S = 3:2.
The result implies that LAST YEAR -- before the 10% increase in R and the 5% increase in S -- there were 3 R voters for every 2 S voters.
To determine R:S THIS YEAR, plug in values for R and S.
Let R last year = 30 and S last year = 20.
This year:
R increased by 10% = (1.1)*30 = 33.
S increased by 5% = (1.05)*20 = 21.
R/(R+S) = 33/(33+21) = 33/54 = 11/18.
For more practice will alligation, check here:
https://www.beatthegmat.com/ratios-fract ... 15365.html
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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